Hello,Originally Posted bykbryant05

you only have to use the formula for solving this equation:

Transform this equation into the vertex form of a parabola:Originally Posted bykbryant05

=

That means: At rainfall of 25'' you'll get the maximum growth of 13.5''

with this equation it isn't necessary to use substitution method but because you are forced to do so, here it is:Originally Posted bykbryant05

Set . Then your equation becomes:

. Now use the formula for solving this quadratic equation and you'll get Z = -8 or z = 7.

So

I'm not certain what you should do here (I mean I don't understand the words) So I'm going to show you what you can possibly do to get a solution:Originally Posted bykbryant05

Calculate the square-root on both sides of this equation:

. So you get:

Greetings

EB