Question 94068
This illustrates a very important and often-times overlooked rule in squaring numbers.
-5*-5=25 but {{{-5^2=-25}}} Check it out on a calculator. Make sure you don't use any brackets. It turns out {{{-5^3}}} and {{{-5^4}}} are negative also.
What's going on here?
Think of -5 as -1*5 and only the the 5 gets squared. 
Use brackets if you want the result to be positive.  eg.{{{(-5)^2=25}}}
Back to your problem:
{{{-5^2+(10*-5)-10=-85}}}
Ed Jones