x^4-10x^2+9

Here is the graph of it: https://www.desmos.com/calculator/ox7g6zpagq

Notice that it comes down to a point twice, meaning it has 2 relative minimums.

x^4 - 10x^2 + 9

Taking the derivative, we have that

4x^3 - 20x  = 0    factoring, we have that

4x ( x^2 - 5)  = 0

Setting each factor to 0  and solving for x produces

x = 0,  x = √ 5,   x = - √ 5

Taking the second derivative, we have

12x^2 - 20

Putting  0  into this produces a negative...so this is a relative max at x =0

Subbing the othertwo values into the second derivative produces positives...so....we have absolute minimums  at  x  = ±√5