So let's solve this. This is going to be 0 when x is equal to 0 itself. This is going to be equal to 0 when, let's see, if we add x to the 4th to both sides, you get x to the 4th is equal to 81. If we take the square root of both sides of this, you get x squared is equal to 9, or so you get x is plus or minus 3. x is equal to plus or minus 3. These are our candidate inflection points. x is equal to 0, x is equal to plus 3, or x is equal to minus 3. What we have to do now is to see whether the second derivative changes signs around these points in order to be able to label them inflection points.