fungsi kuadrat f(×)=ײ-4×+c mempunyai nilai optimum 20 tentukan nilai c!

jawab

f(x) = x² - 4x + c
a= 1
b = - 4
c = c

nilai optimum = 20
D/-4a = 20
D = 20( -4a)
b² - 4ac  = - 80 a
(-4)² - 4(1)(c) = -80 (1)
16 - 4c = - 80
-4c = - 96
c =  24