Решите уравнения: х^4-13 х^2+36=0 и х^ 4-65 х^2+64=0

1) x^4 - 13x^2 + 36 = 0;

x^2 = t ≥0;

t^2 - 13 t + 36 = 0;

D = 169 - 144 = 25 = 5^2;

t1 = 9; ⇒ x^2 = 9; x = + - 3;

t2 = 4; ⇒ x^2 = 4; x = + - 2.

2) x^4 - 65 x^2 + 64 = 0;

x^2 = t ≥ 0;

t^2 - 65 t + 64 = 0;

t1 = 1; ⇒ x^2 = 1; x = + - 1;

t2 = 64; ⇒ x^2 = 64; x = + - 8