Question

X4 + x2 - 20 = 0 помогите

Answer 1

$x^4+x^2-20=0 \\ t= x^2 \\ t^2+t-20=0 \\ D=1+80 = 81 \\ t_1,x_2 = (-1+-9)/2 \\ t_1 = 4 ; t_2 = -5 \\ x^2 = -5 - not_answer \\ x^2 = 4 \\ x = +-2$