A) x=3y-10
y² - (3y-10)y=12
y² - 3y² +10y =12 ⇒ -2y² +10y=12
y² -5y+6 =0 ⇒ (y-2)(y-3)=0
y1 = 2 ; x1 = -4
y2 = 3 ; x2 = -1
Ответ: (-4;2) ; (-1;3)
б) y = 2x - 8
2x² - (2x-8)² =32
2x² - 4x² +32x - 64=32
x² -16x +48 = 0
x1 = 4 ; y1 = 0
x2=12 ; y2 = 16
c) y = 4x-17
2x² - x·(4x - 17) = 33
2x² -4x² +17x = 33
2x² -17x +33=0
x = [17+-√(289 - 4·2·33)]/4 = (17+/-5)/4
x1 = 3 ; y1 = -5
x2 = 5,5 ; y2 = 5
d) x = 2y+7
(2y+7)² -y² =24
3y² +28y +25= 0
y = [-14+/-√(196-3·25)]/3 = (-14+/-11)/3
y1 = -25/3 ; x1 = -29/3
y2 = -1 ; x2 = 5
Ответ: (-9'2/3 ; -8'1/3) ; (5; -1)