Ìèíèñòåðñòâî îáðàçîâàíèÿ
ÑÈÑÒÅÌ ÓÏÐÀÂËÅÍÈß È ÐÀÄÈÎÝËÅÊÒÐÎÍÈÊÈ (ÒÓÑÓÐ)
2003
1(Ò85.ÐÏ). Íàéäèòå ìàòðèöó D=(AC-AB), åñëè
À= 1 0 ,C= 3 4 4 , B= -3 1 4 .
2 -2 1 -3 5 2 -3 4
(Â îòâåò ââåñòè âòîðóþ ñòðîêó ìàòðèöû D.)
Ðåøåíèå:
Ðàçìåðû ìàòðèö À è Ñ ñîãëàñîâàííû, ò.ê. ÷èñëî ýëåìåíòîâ â ñòðîêå ìàòðèöû À ðàâíî ÷èñëó ýëåìåíòîâ â ñòîëáöå ìàòðèöû Â.
à*ñ= 1 0 * 3 4 4 = 1*3+0*1 1*4+0*(-3) 1*4+0*5 = 3 4 4
2 -2 1 -3 5 2*3+(-2)*1 2*4-2*(-3) 2*4-2*5 4 14 -2
À*Â= 1 0 * -3 1 4 = 1*(-3)+0*2 1*1+0*(-3) 1*4+0*4 = -3 1 4
2 -2 2 -3 4 2*(-3)-2*2 2*1-2*(-3) 2*4-2*4 -10 8 0
D=À*Ñ-À*Â= 3 4 4 _ -3 1 4 = 3-(-3) 4-1 4-4 = 6 3 0
4 14 -2 -10 8 0 4-(-10) 14-8 -2-0 14 6 -2
Îòâåò :14 , 6 , -2.
2(3ÒÎ).Âû÷èñëèòå îïðåäåëèòåëü D= 2 2 1 0
1 1 1 0
1 2 2 1
0 3 2 2
Ðåøåíèå:
2 2 1 0
1 1 1 0
1 2 2 1 =
0 3 2 2
Óìíîæèì òðåòüþ ñòðîêó íà (-2) è ñëîæèì ñ ÷åòâ¸ðòîé ñòðîêîé , ðåçóëüòàò çàïèøåì
â ÷åòâ¸ðòóþ ñòðîêó:
2 2 1 0
1 1 1 0
= 1 2 2 1 =
-2 -1 -2 0
Äàííûé îïðåäåëèòåëü ðàçëîæèì ïî ýëåìåíòàì ÷åòâ¸ðòîãî ñòîëáöà :
3+4 2 2 1
= 1*(-1) * 1 1 1 =
-2 -1 -2
Óìíîæèì âòîðóþ ñòðîêó íà (-2) è ñëîæèì ñ ïåðâîé, ðåçóëüòàò çàïèøåì â ïåðâóþ ñòðîêó . Óìíîæèì âòîðóþ ñòðîêó íà 2 è ñëîæèì ñ òðåòüåé , ðåçóëüòàò çàïèøåì â òðåòüþ ñòðîêó .
0 0 -1
= - 1 1 1 = - (-1) 1+3 * (-1) * 1 1 = 1-0 =1;
0 1 0 0 1
Îòâåò: D = 1.
3(598.Ð7).Ðåøèòå ìàòðè÷íîå óðàâíåíèå
1 2 1 1 1 -1
X* 4 3 -2 = 16* -1 2 3
-5 -4 -1 0 -1 -2 .
Ðåøåíèå:
A*X=B , X=A-1 *B
Íàéä¸ì det A:
1 2 1
det A= 4 3 -2 = 1*3*(-1)+1*4*(-4)+2*(-2)*(-5)-1*3*(-5)-2*4*(-1)-1*(-2)*(-4)=
-5 -4 -1
=-19+20+15-8+8=16 ;
det= 16 ≠ 0;
Ñîñòàâèì ìàòðèöó À -1 , îáðàòíóþ ìàòðèöû À:
À1 1 = 3 -2 = -3 –8 = -11
-4 -1
À12 = - 4 -2 = -(-4-10) = 14
-5 -1
À13 = 4 3 = -16+15 = -1
-5 -4
A21 = - 2 1 = -(-2+4) = -2
-4 -1
A22 = 1 1 = -1+5 = 4
-5 -1
A23 = - 1 2 = - (-4+10) = -6
-5 -4
A31 = 2 1 = - 4-3 = -7
3 -2
A32 = - 1 1 = - (-2-4) = 6
–2
A33 = 1 2 = 3 –8 = -5
4 3
-11/16 -2/16 -7/16
À-1 = 14/16 4/16 6/16
-1/16 -6/16 -5/16
-11/16 -2/16 -7/16 1*16 1*16 -1*16
Õ = 14/16 4/16 6/16 * -1*16 2*16 3*16 =
-1/16 -6/16 -5/16 0*16 -1*16 2*16
-11*1+(-2*(-1))+(-7*0) -11*1+(-2*2)+(-7*(-1)) -11*(-1)+(-2*3)+(-7*2)
= 14*1+4*(-1)+6*0 14*1+4*2+6*(-1) 14*(-1)+4*3+6*2 =
-1*1+(-6*(-1))+(-5*0) -1*1+(-6*2)+(-5*(-1)) -1*(-1)+(-6*3)+(-5*2)
-9 -8 -9
= 10 16 10
5 -8 -27
Îòâåò : Õ = : -9 , -8 , -9 : 10 , 16 , 10 : 5 , -8 , -27 .
4(4Ï5).Ïðè êàêîì çíà÷åíèè ïàðàìåòðà p , åñëè îí ñóùåñòâóåò ,
1 2 -2 1
ïîñëåäíÿÿ ñòðîêà ìàòðèöû À = 2 -3 3 2 ÿâëÿåòñÿ ëèíåéíîé êîìáèíàöèåé ïåðâûõ
1 -1 1 2
8 -7 p 11
òð¸õ ñòðîê?
Ðåøåíèå :
Âû÷èñëèì det A:
1 2 -2 1 1 2 -2 1 -7 7 0 -7 7 0
det A = 2 -3 3 2 = 0 -7 7 0 = 3 -3 -1 = 3 -3 -1 =
1 -1 1 2 0 3 -3 -1 23 -16-p -3 14 -7-p 0
8 -7 p 11 0 23 -16-p -3
-1*(-1) 2+3 * -7 7 = 49 + 7p – 98 = 7p - 49
14 -7-p
Åñëè det A=0 , òî ðàíã ìàòðèöû À ðàâåí äâóì , ò.å. 7p – 49 = 0 , p = 7.
Òðåòüÿ ñòðîêà ïî òåîðåìå î áàçèñíîì ìèíîðå ÿâëÿåòñÿ êîìáèíàöèåé ïåðâûõ äâóõ .
Îáîçíà÷èì êîýôôèöèåíòû ýòîé êîìáèíàöèè ÷åðåç λ1 è λ2 , λ3 ,òîãäà (8,-7,7,11) = λ1(1,2,-2,1)+ + λ2 (2,-3,3,2) + λ3 (1,-1,1,2);
Èìååì ñèñòåìó : λ1 + 2λ2 + λ3 = 8 * 2
2λ1- 3λ2 - λ3 = -7
-2λ1 + 3λ2 + λ3 = 7
λ1 + 2λ2 + 2λ3 = 11
Ðåøèì äàííóþ ñèñòåìó ìåòîäîì Ãàóññà :
λ1 + 2λ2 + λ3 = 8 1) λ3 = 3
7λ2 + 3λ3 = 23 2) 7λ2 + 9 = 23
7λ2 + 3λ3 = 23 7λ2 = 14
λ3 = 3 λ2 = 2
3) λ1 + 2*2 + 3 =8
λ1 = 1
êîýôôèöèåíòû ëèíåéíûõ êîìáèíàöèé λ1 = 1 ; λ2 = 2 ; λ3 = 3 ;
Îòâåò : (8,-7,7,11) = 1(1,2,-2,1)+ 2(2,-3,3,2) + 3(1,-1,1,2) .
5. Îòíîñèòåëüíî êàíîíè÷åñêîãî áàçèñà â R3 äàíû ÷åòûðå âåêòîðà f1(1,1,1) , f2 (1,2,3) , f3 (1,3,6), x(4,7,10). Äîêàæèòå, ÷òî âåêòîðû f1, f2 , f3 ìîæíî ïðèíÿòü çà íîâûé áàçèñ â R3 . (ÒÐ0.ÐÏ) . Íàéäèòå êîîðäèíàòû âåêòîðà x â áàçèñå fi .
1 1 1 1 1 1
∆ = 1 2 3 = 0 1 2 = 1*(-1)1+1 * 1 2 = 5 – 4 = 1
1 3 6 0 2 5 2 5
Òàê êàê ∆ ≠ 0 , òî âåêòîðû f1, f2 , f3 îáðàçóþò áàçèñ òð¸õìåðíîãî ïðîñòðàíñòâà R3
Äëÿ âû÷èñëåíèÿ êîîðäèíàò âåêòîðà x â ýòîì áàçèñå ñîñòàâèì ñèñòåìó ëèíåéíûõ óðàâíåíèé :
õ1 + õ2 + õ3 = 4 *(-1)
õ1 + 2õ2 + 3õ3 = 7
õ1 + 3õ2 + 6õ3 = 10
õ1 + õ2 + õ3 = 4
õ2 + 2õ3 = 3 *(-2)
2õ2 + 5õ3 = 6
õ1 + õ2 + õ3 = 4 1) õ3 = 0 3) õ1 + 3 + 0 = 4
õ2 + 2õ3 = 3 2) õ2 + 0 = 3 õ1 = 4 - 3
õ3 = 0 õ2 = 0 õ1 = 1
õ1 = 1 , õ2 = 0 , õ3 = 0 .
Ðåøåíèå ýòîé ñèñòåìû îáðàçóåò ñîâîêóïíîñòü êîîðäèíàò âåêòîðà x â áàçèñå f1, f2 , f3
x(1;3;0);
x = f1 + 3f2 + 0f3;
x = f1 + 3f2 .
Îòâåò : êîîðäèíàòû âåêòîðà x (1;3;0).
6. Äîêàæèòå , ÷òî ñèñòåìà
2õ1 + 2õ2 + õ3 = 8,
õ1 + õ2 + õ3 = 3,
õ1 + 2õ2 + 2õ3 + õ4 = 3,
3õ2 + 2õ3 +2õ4 = 3
èìååò åäèíñòâåííîå ðåøåíèå . (362).Íåèçâåñòíîå õ2 íàéäèòå ïî ôîðìóëàì Êðàìåðà . (0Ì1.ÐË) . Ðåøèòå ñèñòåìó ìåòîäîì Ãàóññà .
Ðåøåíèå:
Ñîñòàâèì ìàòðèöó èç êîýôôèöèåíòîâ ïðè ïåðåìåííûõ
2 2 1 0
À = 1 1 1 0
1 2 2 1
0 3 2 2
Âû÷èñëèì îïðåäåëèòåëü ìàòðèöû À
2 2 1 0 2 2 1 0 2 2 1 1 1 0
∆ = 1 1 1 0 = 1 1 1 0 = (-1)3+4 * 1 1 1 = - 1 1 1 =
1 2 2 1 1 2 2 1 -2 -1 -2 0 1 0
0 3 2 2 -2 -1 -2 0
= - (-1)2+3 * 1 1 = 1
0 1
∆ ≠ 0, òîãäà ñèñòåìà èìååò ðåøåíèå õ2 = ∆ õ2 /∆
2 8 1 0 2 8 1 0 2 8 1 2 8 1
∆ õ2 = 1 3 1 0 = 1 3 1 0 = (-1)3+4 * 1 3 1 = - 1 5 0 =
1 3 2 1 1 3 2 1 -2 -3 -2 0 3 0
0 3 2 2 -2 -3 -2 0
= -(-1)1+3 * 1 5 = ( 3 + 0 ) = 3
0 8
õ2 = 3 /1 = 3.
Ðåøèì ñèñòåìó ìåòîäîì Ãàóññà
2õ1 + 2õ2 + õ3 = 8 *(-2) *(-1)
õ1 + õ2 + õ3 = 3
õ1 + 2õ2 + 2õ3 + õ4 = 3
3õ2 + 2õ3 +2õ4 = 3
õ1 + õ2 + õ3 = 3
- õ3 = 2
õ2 + õ3 + õ4 = 0 *(-3)
3õ2 + 2õ3 +2õ4 = 3
õ1 + õ2 + õ3 = 3
õ2 + õ3 + õ4 = 0
- õ3 - õ4 = 3
õ3 = -2
1) õ3 = - 2 3) õ2 - 2 - 1 = 0
2) 2 - õ4 = 3 õ2 = 3
õ4 = -1 4) õ1 + 3 - 2 = 3
õ1 = 2
Ïðîâåðêà :
2 + 3 – 2 =3, 3 = 3
4 + 3*3 – 2 = 8, 8 = 8
2 + 6 – 4 – 2 = 3, 3 =3
9 – 4 – 2 = 3 , 3 = 3.
Îòâåò : õ1 = 2 , õ2 = 3 , õ3 = - 2 , õ4 = -1.
7. Äàíà ñèñòåìà ëèíåéíûõ óðàâíåíèé
3õ1 + õ2 - õ3 - õ4 = 2,
9õ1 + õ2 - 2õ3 - õ4 = 7,
õ1 - õ2 - õ4 = -1,
õ1 + õ2 - õ3 -3õ4 = -2.
Äîêàæèòå ,÷òî ñèñòåìà ñîâìåñòíà . Íàéäèòå å¸ îáùåå ðåøåíèå . (392.ÁË). Íàéäèòå ÷àñòíîå ðåøåíèå , åñëè õ4 = 1 .
Äîêàçàòåëüñòâî :
Ñèñòåìà ëèíåéíûõ óðàâíåíèé ñîâìåñòíà òîãäà è òîëüêî òîãäà , êîãäà ðàíã îñíîâíîé ìàòðèöû
ñèñòåìû ðàâåí ðàíãó ðàñøèðåííîé ìàòðèöû .
Ñîñòàâèì ðàñøèðåííóþ ìàòðèöó :
3 1 -1 -1 2 0 -2 2 8 8 0 0 1 6 7
À = 9 1 -2 -1 7 → 0 -8 7 26 25 → 0 0 3 18 21 =0
1 -1 0 -1 -1 0 -2 1 2 1 0 -2 1 2 1
1 1 -1 -3 -2 1 1 -1 -3 -2 1 1 -1 -3 -2
Ïåðâàÿ è âòîðàÿ ñòðîêà ïðîïîðöèîíàëüíû ñëåäîâàòåëüíî À = 0. Ïîýòîìó ðàíã ìàòðèöû è ðàñøèðåííîé ìàòðèöû ðàâíû 3 ïîýòîìó ñèñòåìà ÿâëÿåòñÿ ñîâìåñòíîé .
Ðåøèì ñèñòåìó ìåòîäîì Ãàóññà :
çàïèøåì ïîñëåäíåå óðàâíåíèå íà ïåðâîå ìåñòî :
õ1 + õ2 - õ3 -3õ4 = -2
3õ1 + õ2 - õ3 - õ4 = 2
9õ1 + õ2 - 2õ3 - õ4 = 7
õ1 - õ2 - õ4 = -1
1 1 -1 -3 -2 1 1 -1 -3 -2 1 1 -1 -3 -2
Ñ = 3 1 -1 -1 2 → 0 2 -2 -8 -8 → 0 2 -2 -8 -8 →
9 1 -2 -1 7 0 8 -7 -26 -25 0 0 -1 -6 -7
1 -1 0 -1 -1 0 2 -1 -2 -1 0 0 -1 -6 -7
õ1 + õ2 - õ3 -3õ4 = -2
→ 2õ2- 2õ3 -8õ4 = -8
- õ3 -6õ4 = -7.
1) õ3 = 7 - 6õ4
2) õ2 - õ3 -4õ4 = -4
õ2 = õ3 + 4õ4 - 4
õ2 = 7 - 6õ4 + 4õ4 - 4
õ2 = 3 - 2õ4
3) õ1 = - õ2 + õ3 + 3õ4 - 2
õ1 = - 3 + 2õ4 + 7 - 6õ4 + 3õ4 – 2
õ1 = 2 -õ4 .
Ïîëó÷àåì îáùåå ðåøåíèå ñèñòåìû :
õ1 = 2 -õ4
õ2 = 3 - 2õ4
õ3 = 7 - 6õ4.
Íàéä¸ì ÷àñòíîå ðåøåíèå , åñëè õ4 = 1 òîãäà
õ1 = 2 – 1 = 1;
õ2 = 3 – 2*1 = 1;
õ3 = 7 – 6*1 =1.
Îòâåò : (1;1;1;1) – ÷àñòíîå ðåøåíèå .
8. Äàíà ñèñòåìà ëèíåéíûõ îäíîðîäíûõ óðàâíåíèé
2õ1 +3õ2 - õ3 - õ4 + õ5 = 0,
3õ1 - 2õ2 - 3õ3 -3õ5 = 0,
õ1 - 3õ2 + 2õ3 -5õ4 -2õ5 = 0.
Äîêàæèòå , ÷òî ñèñòåìà èìååò íåòðèâèàëüíîå ðåøåíèå . Íàéäèòå îáùåå ðåøåíèå ñèñòåìû . Íàéäèòå êàêóþ-íèáóäü ôóíäàìåíòàëüíóþ ñèñòåìó ðåøåíèé Äîêàçàòåëüñòâî :
Ñèñòåìà èìååò íåòðèâèàëüíîå ðåøåíèå òîãäà è òîëüêî òîãäà , êîãäà ðàíã å¸ ìàòðèöû ìåíüøå ÷èñëà íåèçâåñòíûõ . ýòîì ñëó÷àå ðàíã ìàòðèöû íå áîëüøå òð¸õ , à ïåðåìåííûõ â ñèñòåìå ïÿòü .
Ðåøèì ñèñòåìó ìåòîäîì Ãàóññà .
Çàïèøåì ìàòðèöó ñèñòåìû :
2 3 -1 -1 1 1 -3 2 -5 -2
À = 3 -2 3 0 -3 → 0 9 -5 9 5 │*7 →
1 -3 2 -5 -2 0 7 -3 15 3 │*(-9)
1 -3 2 -5 -2
→ 0 9 -5 9 5
0 0 -8 -72 8
õ1 -3õ2 + 2õ3 - 5õ4 -2õ5 = 0
9õ2 - 5õ3 + 9õ4 +5õ5 = 0
-8õ3 -72õ4 +8õ5 = 0
1) 8õ3 = -72õ4 + 8õ5
õ3 = - 9õ4 + õ5
2) 9õ2 + 45õ4 - 5õ5 + 9õ4 +5õ5 = 0
9õ2 + 36õ4 = 0
õ2= - 4õ4
3) õ1 +12õ4 - 18õ4 + 2 õ5 - 5õ4 -2õ5 = 0
õ1 - 11õ4 = 0
õ1 =11õ4
Îáùåå ðåøåíèå ñèñòåìû :
õ1 =11õ4
õ2= - 4õ4
õ3 = - 9õ4 + õ5
Íàéä¸ì ôóíäàìåíòàëüíóþ ñèñòåìó ðåøåíèé , ïîëîæèâ õ4 = 1 , õ5 = 0.
õ1 =11*1 = 11,
õ2= - 4*1 = -4,
õ3 = - 9*1 + 0 = -9.
Ïóñòü õ4 = 0, õ5 = 1.
õ1 =11*0 = 0,
õ2= - 4*0 = 0,
õ3 = - 9*0 + 1 = 1.
Îòâåò : (11;-4;-9;1;0)
(0; 0; 1; 0; 1).
9 (3ÑÀ). Íàéäèòå ïëîùàäü ïàðàëëåëîãðàììà , ïîñòðîåííîãî íà âåêòîðàõ à = 2ð + 3r, b = p –2r , | p | = √2 , | r | = 3, (p,^r) = 45° .
Ðåøåíèå :
S =| [à , b] | = | [2ð + 3r , p –2r] | = | 2[p , p] - 4[p, r ] + 3[r , p] -6[r , r] |
[p , p] = 0 , [r , r] = 0 , [r , p] = - [p, r ] .
S = | 7[r , p] | = 7| r | * | p | * sinφ
S = 7 * 3 * √2 * sin 45° = 21 * √2 * √2 / 2 =21 .
Îòâåò :S =21 .
10 (78Ò). Âû÷èñëèòå ÏðBD[BC ,CD] , åñëè B(6,3,3) ; C(6,4,2) ; D(4,1,4) .
Ðåøåíèå :
Íàéä¸ì êîîðäèíàòû âåêòîðîâ
BD = ( 4 – 6 , 1 – 3 , 4 – 3 ) = ( - 2 ; - 2 ; 1 ),
BC = ( 6 – 6 , 4 – 3 , 2 – 3 ) = ( 0 ; 1 ; - 1 ),
CD = ( 4 – 6 , 1 – 4 , 4 – 2 ) = ( - 2 ; - 3 ; 2 ).
Íàéä¸ì âåêòîðíîå ïðîèçâåäåíèå :
i j k
[BC ,CD] = 0 1 -1 = i (2 – 3) – j (0 –2) + k (0 + 2) = - i + 2j + 2k .
-2 -3 2
Ïóñòü [BC ,CD] = à , òîãäà à = ( -1 ; 2 ; 2 )
ÏðBD à = ( BD , a ) /| BD |
( BD , a ) = -2*( -1 ) – 2*2 + 1*2 = 2 –4 + 2 = 0 .
ÏðBD à = 0 .
Îòâåò : ÏðBD à = 0 .
11. Ëèíåéíûé îïåðàòîð À äåéñòâóåò â R3 → R3 ïî çàêîíó Ax = (- õ1 + 2õ2 + x3 , 5õ2 , 3õ1 + 2õ2 + õ3 ), ãäå õ( õ1, õ2, õ3 ) – ïðîèçâîëüíûé âåêòîð .(125.ÐÏ). Íàéäèòå ìàòðèöó À ýòîãî îïåðàòîðà â êàíîíè÷åñêîì áàçèñå . Äîêàæèòå , ÷òî âåêòîð õ(1,0 ,3) ÿâëÿåòñÿ ñîáñòâåííûì äëÿ ìàòðèöû À .(Ò56). Íàéäèòå ñîáñòâåííîå ÷èñëî λ0 , ñîîòâåòñòâóþùåå âåêòîðó õ . (Ä25.ÐÏ). Íàéäèòå äðóãèå ñîáñòâåííûå ÷èñëà , îòëè÷íûå îò λ0 . Íàéäèòå âñå ñîáñòâåííûå âåêòîðû ìàòðèöû À è ñäåëàéòå ïðîâåðêó .
Ðåøåíèå :
Ax = (- õ1 + 2õ2 + x3 ; 5õ2 ; 3õ1 + 2õ2 + õ3 )
Íàéä¸ì ìàòðèöó â áàçèñå l1 , l2 , l3
A l1 = (-1 ; 2 ;1)
A l2 = (0 ; 5 ; 0)
A l3 = (3 ; 2 ; 1)
-1 2 1
A = 0 5 0
3 2 1 .
Äîêàæåì , ÷òî âåêòîð õ = (1 ,0 ,3) ÿâëÿåòñÿ ñîáñòâåííûì äëÿ ìàòðèöû À.
Èìååì
-1 2 1 1 -1 + 0 + 3 2 1
Aõ = 0 5 0 * 0 = 0 + 0 + 0 = 0 = 2 * 0
3 2 1 3 3 + 0 + 3 6 3 .
Îòñþäà ñëåäóåò , ÷òî âåêòîð õ = (1 ,0 ,3) ñîáñòâåííûé è îòâå÷àåò ñîáñòâåííîìó ÷èñëó λ = 2 .
Ñîñòàâëÿåì õàðàêòåðèñòè÷åñêîå óðàâíåíèå :
-1 – λ 2 1
0 5 – λ 0 = 0
3 2 1 – λ
(5 – λ)*((-1 – λ)*(1 – λ) – 3) = 0
5 – λ = 0 èëè λ2 –1 – 3 = 0
λ2 = 4
λ = ±2
λ1 = 2 , λ2 = -2 , λ3 = 5 .
õ1 + 2õ2 + õ3 = 0 õ2 = 0
7õ2 = 0
3õ1 + 2õ2 + 3õ3 = 0
õ1 + õ3 = 0 õ1 = -õ3
3õ1 + 3õ3 = 0
Ïóñòü õ3 = 1 ,òîãäà õ1 = -1 , èìååì ñîáñòâåííûé âåêòîð õ1 = (-1 ;0 ;1) .
Ïðîâåðêà :
-1 2 1 -1 1 + 0 + 1 2 -1
A = 0 5 0 * 0 = 0 + 0 + 0 = 0 = -2 * 0
3 2 1 1 -3 + 0 + 1 -2 1
Ñëåäîâàòåëüíî , õ1 = (-1 ;0 ;1) ñîáñòâåííûé âåêòîð è îòâå÷àåò ñîáñòâåííîìó ÷èñëó λ = -2.
-6õ1 + 2õ2 + õ3 = 0
3õ1 + 2õ2 - 4õ3 = 0
-9õ1 + 5õ3 = 0
õ1 = 5/9 õ3
-6*(5/9 õ3) + 2õ2 + õ3 = 0
-10/3 õ3 + õ3 + 2õ2 = 0
2õ2 = 7/3 õ3
õ2 = 7/6 õ3 .
Ïóñòü õ3 = 18 , òîãäà õ1 = 10 , õ2 = 21 .
Âåêòîð õ2 = (10 ;21 ;18) ñîáñòâåííûé âåêòîð .
Ïðîâåðêà
-1 2 1 10 -10 + 42 + 18 50 10
A = 0 5 0 * 21 = 0 + 105 + 0 = 105 = 5 * 21
3 2 1 18 30 + 42 + 18 90 18 .
Îòâåò : ìàòðèöà â êàíîíè÷åñêîì áàçèñå : -1 , 2 , 1 : 0 , 5 , 0 : 3 , 2 , 1; âåêòîð õ = (1 ,0 ,3) ñîáñòâåííûé è îòâå÷àåò ñîáñòâåííîìó ÷èñëó λ = 2 , õ1 = (-1 ;0 ;1) ñîáñòâåííûé âåêòîð è îòâå÷àåò ñîáñòâåííîìó ÷èñëó λ = -2 , õ2 = (10 ;21 ;18) ñîáñòâåííûé è îòâå÷àåò ñîáñòâåííîìó ÷èñëó λ = 5 .
Ðåøåíèå :
Íàéä¸ì óãëîâîé êîýôôèöèåíò ïðÿìîé 2õ + 3y + 5 = 0.
3y = -2x –5
y = -2/3 x – 5/3
κ = -2/3
Òàê êàê èñõîäíàÿ ïðÿìàÿ ïàðàëëåëüíà äàííîé , òî å¸ óãëîâîé êîýôôèöèåíò ðàâåí κ = -2/3 .
Óðàâíåíèå ïðÿìîé èìåþùåé óãëîâîé êîýôôèöèåíò κ è ïðîõîäÿùåé ÷åðåç òî÷êó Ì(õ0,y0) çàïèñûâàåòñÿ â âèäå
y – y0 = κ(x – x0).
Èìååì
y – 4 = -2/3 (x – 1)
3y – 12 = -2x + 2
2õ + 3y - 14 = 0.
Îòâåò : 2õ + 3y - 14 = 0 – óðàâíåíèå èñêîìîé ïðÿìîé .
13(3À2.ÐÏ).Íàéäèòå êîîðäèíàòû ïðîåêöèè òî÷êè Ì(3,6) íà ïðÿìóþ õ + 2y – 10 = 0.
Ðåøåíèå :
Ïóñòü N – ïðîåêöèÿ òî÷êè Ì íà äàííóþ ïðÿìóþ .
Ñîñòàâèì óðàâíåíèå ïðÿìîé MN óãëîâîé êîýôôèöèåíò çàäàííîé ïðÿìîé õ + 2y – 10 = 0 ðàâåí κ1 = -1/2 , òîãäà óãëîâîé êîýôôèöèåíò ïðÿìîé MN ðàâåí κ2 = 2 .
Òîãäà óðàâíåíèå MN èìååò âèä y – y0 = 2(x – x0) .
Äëÿ îïðåäåëåíèÿ êîîðäèíàò òî÷êè N ðåøèì ñèñòåìó óðàâíåíèé
õ + 2y – 10 = 0
y – y0 = 2(x – x0) , x0 = 3 , y0 = 6 .
õ + 2y – 10 = 0 2õ + 4y – 20 = 0
y – 6 = 2(x – 3) -2õ + y = 0
4y = 20
y = 4
2õ = y
õ = ½ y
õ = ½ * 4 = 2
õ = 2 .
Îòâåò : êîîðäèíàòû ïðîåêöèè òî÷êè Ì(3,6) íà ïðÿìóþ õ + 2y – 10 = 0 N(2,4).
14(103.ÁË). Çàïèøèòå îáùåå óðàâíåíèå ïëîñêîñòè , ïîõîäÿùåé ÷åðåç òðè çàäàííûå òî÷êè M1(-6,1,-5) , M2(7,-2,-1) , M3(10,-7,1) .
Ðåøåíèå :
Óðàâíåíèå ïëîñêîñòè , ïðîõîäÿùåé ÷åðåç 3 òî÷êè èìååò âèä
x-x1 y-y1 z-z1
x2-x1 y2-y1 z2-z1 = 0
x3-x1 y3-y1 z3-z1
x-6 y-1 z+5
7+6 -2-1 -1+5 = 0
10+6 -7-1 1-5
x-6 y-1 z+5
13 -3 4 = 0
16 -8 -4
(x –6)* -3 4 - (y – 1)* 13 4 + (z + 5)* 13 -3 = (x –6)*(12+32) – (y – 1)*(-52-64)+
-8 -4 16 -4 16 -8
+ (z + 5)*(-104+48) = 0
(x –6)*44 - (y – 1)*(-116) + (z + 5)*(-56) = 0
11*(x –6) + 29*(y – 1) – 14*(z + 5) = 0
11x – 66 + 29y – 29 – 14z – 70 = 0
11x + 29y – 14z – 165 = 0 .
Îòâåò : îáùåå óðàâíåíèå ïëîñêîñòè 11x + 29y – 14z – 165 = 0 .
15.Äàíà êðèâàÿ 4x2 – y2 – 24x + 4y + 28 = 0 .
8.1.Äîêàæèòå , ÷òî ýòà êðèâàÿ – ãèïåðáîëà .
8.2 (325.Á7).Íàéäèòå êîîðäèíàòû å¸ öåíòðà ñèììåòðèè .
8.3 (Ä06.ÐÏ).Íàéäèòå äåéñòâèòåëüíóþ è ìíèìóþ ïîëóîñè .
8.4 (267.ÁË). Çàïèøèòå óðàâíåíèå ôîêàëüíîé îñè .
8.5. Ïîñòðîéòå äàííóþ ãèïåðáîëó .
Ðåøåíèå :
Âûäåëèì ïîëíûå êâàäðàòû
4(x2 – 6x + 9) – 36 – (y2 – 4y + 4) + 4 + 28 = 0
4(x – 3)2 – (y – 2)2 – 4 = 0
4(x – 3)2 – (y – 2)2 = 4
((x – 3)2/1) – ((y – 2)2/4) = 1
Ïîëîæèì x1 = x – 3 , y1 = y – 2 , òîãäà x12/1 – y12/4 =1 .
Äàííàÿ êðèâàÿ ÿâëÿåòñÿ ãèïåðáîëîé .
Îïðåäåëèì å¸ öåíòð
x1 = x – 3 = 0 , x = 3
y1 = y – 2 = 0 , y = 2
(3 ; 2) - öåíòð .
Äåéñòâèòåëüíàÿ ïîëóîñü a =1 .
Ìíèìàÿ ïîëóîñü b =2 .
Óðàâíåíèå àñèìïòîò ãèïåðáîëû
y1 = ± b/a x1
(y – 2) = (± 2/1)*(x – 3)
y –2 = 2x – 6 è y – 2 = -2(x – 8)
2x – y – 4 = 0 2x + 2y – 8 = 0
x + y – 4 = 0 .
Îïðåäåëèì ôîêóñû ãèïåðáîëû
F1(-c ; 0) , F2(c ; 0)
c2 = a2 + b2 ; c2 = 1 + 4 = 5
c = ±√5
F1(-√5; 0) , F2(√5 ; 0).
F1′(3 - √5; 2) , F2′ (3 + √5; 2).
Óðàâíåíèå F1′ F2′ (x – 3 + √5) / (3 + √5 – 3 + √5) = (y – 2) /(2 – 2) ; y = 2
Îòâåò: (3 ; 2) , äåéñòâèòåëüíàÿ ïîëóîñü a =1 , ìíèìàÿ ïîëóîñü b =2, (x – 3 + √5) / (3 + √5 – 3 + √5) = (y – 2) /(2 – 2) ; y = 2 .
16.Äàíà êðèâàÿ y2 + 6x + 6y + 15 = 0.
16.1.Äîêàæèòå , ÷òî ýòà êðèâàÿ – ãèïåðáîëà .
16.2(058.ÐÏ). Íàéäèòå êîîðäèíàòû å¸ âåðøèíû .
16.3(2Ï9). Íàéäèòå çíà÷åíèÿ å¸ ïàðàìåòðà p .
16.4(289.ÐÏ). Çàïèøèòå óðàâíåíèå å¸ îñè ñèììåòðèè .
16.5.Ïîñòðîéòå äàííóþ ïàðàáîëó .
Ðåøåíèå :
Âûäåëèì ïîëíûé êâàäðàò ïðè ïåðåìåííîé y
(y2 + 6y + 9) + 6x + 6 = 0
(y + 3)2 = - 6(x + 1) .
Ïîëîæèì y1 = y + 3 , x1 = x + 1 .
Ïîëó÷èì
y12 = ±6x1 .
Ýòî óðàâíåíèå ïàðàáîëû âèäà y2 = 2px , ãäå p = -3 .
Äàííàÿ êðèâàÿ ÿâëÿåòñÿ ãèïåðáîëîé .
Òàê êàê p<0 , òî âåòâè ïàðàáîëû â îòðèöàòåëüíóþ ñòîðîíó. Êîîðäèíàòû âåðøèíû ïàðàáîëû y + 3 = 0 x + 1 = 0
y = -3 x = -1
(-1 ; -3) – âåðøèíà ïàðàáîëû .
Óðàâíåíèå îñè ñèììåòðèè y = -3.
Îòâåò : (-1 ; -3) – âåðøèíà ïàðàáîëû , p = -3 , óðàâíåíèå îñè ñèììåòðèè y = -3 .