[Math] If polynomial $ax^4 +bx^2 +c$ has four real roots

Question

A polynomial $ax^4 + bx^2 + c$ where $a,b,c$ are positive while $x$ is a
real variable, does it have four real roots or 2 real roots? Is there any formula or way to find how many real roots this polynomial has?

Answer 1

If a, b, and c are positive, and x is real, then the whole expression is positive, and thus it has no real roots.