Answer:
x = 4 and x = -4
x = 1 and x = -1
Step-by-step explanation:
let u = x^2
Then,
u^2-5u+4 = 0
(u - 4)(u - 1) = 0
u = 4 and u = 1
we substitute back for u
x^2 = 4
x^2 = 1
