# Math Help - Strange number in otherwise normal equation

1. ## Strange number in otherwise normal equation

Greetings, I have an example of a question and answer I am trying to use to understand how to do this type of problem. But I can't understand where they are getting the number 0.21h! Please see attachment for full problem. Thanks so much!

2. $-0.001(105+h)^2
$

square the binomial, note the pattern ... $\textcolor{red}{(a+b)^2 = a^2 + 2ab + b^2}$

$-0.001(105^2 + 2(105)h + h^2)$

$-0.001(11025 + 210h + h^2)$

$-(11.025 + 0.21h + 0.001h^2)$

3. Thank you ever so much! I learned something long forgotten, you're the best!