X⁴+5x²-6=0 solve for x

Let u = x², then we would have u² + 5u - 6 = 0

From here, we can factor it and get us (u-1) (u+6) = 0

So our solution for u is u = - 6 or 1.

Now substitute u back to x².

x² = - 6 or 1

x = ±√ (-6) or ±√1

Since ±√ (-6) is not real number, we ignore it.

Which leave us x = ±√1 = ±1

So our real solution is x = - 1 or 1.