gan ini caranya gmna yang detail ya,,, #makasih

f (x) = ax^2 +2x +4a
f' (x) = 2ax +2
Nilai maksimum didapat dari f' (x) = 0
2ax + 2 = 0
2ax = -2
ax = -1
x = -1/a
f (-1/a) = 3
a(-1/a)^2 +2(-1/a) +4a = 3
a + -2/a +4a = 3
5a - 2/a = 3
(5a^2 -2)/a = 3
5a^2 -2 = 3a
5a^2 - 3a -2 = 0
(5a +2)(a - 1) = 0
5a + 2 = 0 atau a - 1 = 0
a = -2/5 atau a = 1....(2)