Grafik fungsi f(x)=(a+1)×^2+(5a+2)×-36 mempunyai sumbu simetri x=-2 nilai ekstrem fungsi ini

F(x) = (a + 1)x² + (5a + 2)x – 36

a = a + 1
b = 5a + 2
c = -36

sumbu simetrik ketika x = -b/2a
-2 = -(5a + 2)/2(a + 1)
-2 = -(5a + 2)/(2a + 2)
2 = (5a + 2)/(2a + 2)
2(2a + 2) = 5a + 2
4a + 4 = 5a + 2
5a – 4a = 4 – 2
a = 2

sehingga, fungsi akan menjadi :

f(x) = (2 + 1)x² + (5(2) + 2)x – 36
f(x) = 3x² + 12x – 36

nilai ekstrim = f(-2)
f(-2) = 3(-2)² + 12(-2) – 36
= 12 – 24 – 36
= -48