How do you use the rational root theorem to find the roots of #x^4 - 7x^2 + 12 = 0#?
Trying a few substitutions, we quickly find that
So the only rational roots are
George C gives a great answer to find that
If you need to find all (real or complex) roots, there a bit more work to do.
Divide by the factors using synthetic division or long division. Or divide by the product of these 2 factors,
So the roots are: