I was doing a problem when I got suddenly stuck with a middle term factorisation.
The equation is as follows:
$$x^4-289x^2+14400=0.$$
I managed to somehow solve it, but it took a lot of time.
Can you please help me with a fast way if any, or can you at least tell me what is the fastest method you know?
Thank you.
A direct method would be to let $y=x^2$,
and solve $y^2-289y+14400=0$ using the quadratic formula.