* = -7
у= -7х - 5
-------------------------
1-cos^2a+ sin^2a/cos^2a * cos^2a
сокращаем cos^2a
sin^2a+cos^2a-cos^2a+sin^2a= 2sin^2a;
б) sin^2a+cos^2a-sin^2a+cos^2a= 2cos^2a
2ab(4a+8)-7b(3a²+2a)=8а²b+16ab-21a²b-14ab=-13a²b+2ab
Xy = - 30
x = 1 - y
(1 - y) y + 30 = 0
y - y^2 + 30 = 0
y^2 - y - 30 = 0
D = 1 + 120 = 121
y1 = ( 1 + 11)/2 = 12/2 = 6
y2 = ( 1 - 11)/2 = - 10/2 = - 5
x1 = 1 - y1 = 1 - 6 = - 5
y1 = 6
x2 = 1 - y1 = 1 + 5 = 6
y2 = - 5
Ответ
( - 5; 6) ;
(6 ; - 5)