Question

Bila fungsi f(x) = 2x²+6x-c mempunyai nilai minimum 3, maka nilai c adalah...
a. -6,5
b. -6
c. -7,5
d. -8
Dijawabnya dengan uraian, terima kasih!

Answer 1

Jawab

f(x) = 2x² +6x - c

x = -b/2a
x = -6/2(2)
x = - 6/4
x = - 3/2

f(-3/2) = 3
2(-3/2)² +6(-3/2) c c= 3
2(9/4) - 9 - c = 3
18/4 - 9 - c = 3

c=  18/4 - 9 - 3
c = - 7,5