jika fungsi f(x)=-2x^2-(a+1)x+2a mempunyai nilai maksimum 8, maka nilai a=...

f(x) = -2x²-(a+1)x+2a
x(maks) = -b/2a = a+1/-4
f(x maks) = -2((a+1)²/16)-(a+1)²/-4+2a=8
Misal H=a+1
f(H)= -2(H²/16)+(H²/4)+2(H-1)=8
= (H²/8)+2H=10
= H²+16H=80
= (H+20)(H-4)=0
H(1)= -20 ; a= -21
H(2)= 4 ; a= 3