How do you solve this?

X⁴-13x²+36
(x²-4)(x²-9)

x²=4. | x²=9
x=√4. |x=√9
x=2. |x=3

27x³-8=0
x³=8/27
x=2/3

...

View this equation as a quadratic like so:


We can factor just like a normal quadartic!
We want two numbers that multiply to 36x² and add to -13x.
These numbers are -9x and -4x.
Because our leading coefficient is 1, we can factor straight to (x²-4)(x²-9).
Here's what it would look like if we split the middle and factored:


Of course, any value which causes either factor to equal zero is a solution.
The other factor times zero is still going to be zero, of course.
Let's derive these two possibilities from our equation.

We can add that constant to the right side...

And take the square root of each side.


So, your possible x values are
2, -2, 3, and -3.