?

To use the quadratic function, one side must be equal to 0. Did your question not include an equality? You can't find the value of x without having the function equal something (and if you did have any value instead of 0, you could bring it to the x side to get 0); Even if you simplify that down to the form , you don't know what that function is equal to, x could have an infinite number of possibilities. Otherwise I'd say your instructor wants you to assume it is equal to 0 and do as you are planning to.