X^2 - 2x - 8 = 0
D = 4 + 4*8 = 32 + 4 = 36 = 6^2
x1 = ( 2 + 6)/2 = 8/2 = 4;
x2 = ( 2 - 6)/2 = - 4/2 = - 2
У=-5х
х-4у=-18
х-4*(-5х)=-18
х+20х=-18
х=-18/21
х=-6/7
у=-5*(-6/7)=30/7
ответ: (-6/7;30/7)
2 - X = X/9
9( 2 - X ) = X
18 - 9x = X
10x = 18
X = 1,8
Ответ:
(-3авс)в 3-ей= -27*a3*b3*c3