✔ 最佳答案
If i answer this choose me a best answer
let -9 turn to the left so
x^4+10x^2+9=0
let y=x^2
so subt.
y^2+10y+9=0
(y+1)(y+9)=0
y=-1 and -9
since y=x^2
x^2=-9 and -1
the answer is x=+-3i and +-1i
imaginary
u can search more about like trigonometric imagineries in complex number