SBMPTN 2014 kode 552

log(4^x + a.2^x + a + 3) = log(2^(2x) + a.2^x + a + 3)
Misal, 2^x = p, maka :

f(x) = log(p^2 + ap + a + 3)

Agar nilainya selalu real, maka Diskriminannya ≤ 0
a = 1, b = a, c = a + 3

b^2 - 4ac ≤ 0
a^2 - 4(1)(a + 3) ≤ 0
a^2 - 4a - 12 ≤ 0
(a - 6)(a + 2) ≤ 0

-2 ≤ a ≤ 6

untuk a