Hello, kingkaisai2!

Edit: I corrected my wrong sign below ... Sorry for any confusion it caused.

I don't know what methods you've been taught . . .

Find the roots of the equation

Let , where and are real.

We have: .

Then: .+

Equate real and imaginary components: .

From (2), we have: .

Substitute into (1): .

Multiply by

Factor: .

We have two equations to solve:

. .

. .

Substitute into (2): .

Therefore: .