Question

( x +2) *( x-2) * ( x+1) * ( x-1) + 5x² = 20 ?

Answer 1

(x + 2) (x - 2) (x + 1) (x - 1) + 5x² = 20
(x² + 2x - 2x - 4) (x² + x - x -1) + 5x² = 20
(x² - 4) (x² - 1) + 5x² = 20
x^4 - x² - 4x² + 4 + 5x² = 20
x^4 - 5x² + 4 + 5x² = 20
x^4 + 4 = 20