SOLUTION: Please help us solve for f. Original problem was {{{f(x)=x^2-9}}} We simplified this to {{{f(x)-x^2+9=0}}} but do not know were to go from here. Thank you, Keith

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Please help us solve for f. Original problem was {{{f(x)=x^2-9}}} We simplified this to {{{f(x)-x^2+9=0}}} but do not know were to go from here. Thank you, Keith      Log On


   

Question 147363: Please help us solve for f. Original problem was f%28x%29=x%5E2-9
We simplified this to f%28x%29-x%5E2%2B9=0 but do not know were to go from here.
Thank you, Keith
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Do you mean solve for f(x)? The equation is already solved for f(x). I'm assuming that you want to solve for x



f%28x%29=x%5E2-9 Start with the given equation


0=%28x%2B3%29%28x-3%29 Plug in f%28x%29=0


0=%28x%2B3%29%28x-3%29 Factor the right side


Now set each factor equal to zero:

x%2B3=0 or x-3=0


x=-3 or x=3 Now solve for x in each case


So our answers are

x=-3 or x=3