Question

х^2+ах-20=0 ,якщо х=-4​

Answer 1

-4²+a*(-4)-20=0

-16+a*(-4)-20=0

-16-4a-20=0

4a=-36

a=-9

Answer 2

$x^{2} +ax-20=0,x=-4:\\(-4)^{2} +a*(-4)-20=0;\\16-4a-20=0;\\-4-4a=0;\\-4a=4;\\a=4:(-4);\\a=-1.\\Otvet:-1.$