# Math Help - Functions problem

1. ## Functions problem

Problem: The graph below shows the function g, where g(x) = k(x+3)(x-3) for some constant k. If g(a-1.2)=0 and a>0, what is the value of a?

2. Originally Posted by yety124
Graph: http://i55.tinypic.com/amtdsy.jpg

Problem: The graph above shows the function g, where g(x) = k(x+3)(x-3) for some constant k. If g(a-1.2)=0 and a>0, what is the value of a?
If you plug a-1.2 in for x, you get $g(a-1.2) = k((a-1.2)+3)((a-1.2)-3) = k(a+1.8)(a-4.2)=0$. So either $a+1.8=0$ or $a-4.2=0$; however, a>0...so which answer will it be?