How would you find how many turning points if given an equation with out graphing?

ex. f(x) =22x^4 - 4x^3 + 3x^2 - 2x + 2

Edit:

i think i got it. All you need to do is take the highest exponent and subtract 1, giving you the # of turning points for that function.

In this case it would be 4-1 = 3. There fore f(x) has 3 turning points.