The thing to remember about functions is that they do the same thing to whatever is inside the parentheses. So don’t worry about the *r* vs. the *h*. They could use *x*, or a little star symbol, or whatever else they want. What matters is that the function *f*, as defined here, will equal zero when *r* = 4, or when *r* = –1.

When we’re told that *f*(*h* – 3) = 0, we can conclude that *h* – 3 must equal either 4 or –1. Therefore, h must equal either 7 or 2.

The graph below might help show what’s going on visually. When the thing in the parentheses next to the *f* (also known as the argument of the function) equals –1 or 4, the function equals zero. Therefore *h* – 3 must equal –1 or 4.

from Tumblr https://ift.tt/2OToWai