Помогите решить уравнение 9х^4-82х^2+9=0

X^2 = A ; A > 0 ------------ 9A^2 - 82A + 9 = 0 D = 6724 - 324 = 6400 ; √ D = 80  A1 = ( 82 + 80 ) : 18 = 9  A2 = ( 82 - 80 ) : 18 = 2/18 = 1/9  ---------------- X^2 = 9  X1 = 3  X2 = - 3  --------------- X^2 = 1/9  X3 = 1/3  X4 = - 1/3