Jika bilangan real x memenuhi 2^x + 2^-x = 3, maka 4^x + 4^-x = (^ berarti pangkat)

Misal
2^x = a
2^(-x) = b

a+b = 3
ab = 1

4^x + 4^-x = a² + b²
4^x  + 4^-x =  (a+b)² – 2 ab = (3²) – 2(1) = 7

(2^x + 2^(-x)) = 3
(2^x + 2^(-x))^2 = 3^2
2^(2x) + 2.2^x.2^(-x) + 2^(-2x) = 9
2^(2x) + 2 + 2^(-2x) = 9
2^(2x) + 2^(-2x) = 9 – 2
2^(2x) + 2^(-2x) = 7
(2^2)^x + (2^2)^(-x) = 7
4^x + 4^(-x) = 7