SOLUTION: Can you help me on these two questions? If {{{ f(x)= x^2+4x }}} f(x)=7, x= ? f(x)-6, x= ?

Algebra ->  Functions -> SOLUTION: Can you help me on these two questions? If {{{ f(x)= x^2+4x }}} f(x)=7, x= ? f(x)-6, x= ?      Log On


   

Question 54517: Can you help me on these two questions? If +f%28x%29=+x%5E2%2B4x++
f(x)=7, x= ?
f(x)-6, x= ?
Answer by rchill(405) About Me  (Show Source):
You can put this solution on YOUR website!
Using substitution we get f(7)=7%5E2%2B4%2A7, which simplifies to 49%2B28 which reduces to 77. Similarly, f(-6)=%28-6%29%5E2%2B4%2A%28-6%29, which simplifies to 36-24, which reduces to 12.