SOLUTION: Find the value of the polynomial {{{-x^2+10x-10}}} when x=-5 i want to make sure i did this correctly. {{{-(-5^2)+10(-5)-10}}} {{{25-50-10}}} answer -35

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find the value of the polynomial {{{-x^2+10x-10}}} when x=-5 i want to make sure i did this correctly. {{{-(-5^2)+10(-5)-10}}} {{{25-50-10}}} answer -35      Log On


   

Question 94068: Find the value of the polynomial -x%5E2%2B10x-10 when x=-5
i want to make sure i did this correctly.
-%28-5%5E2%29%2B10%28-5%29-10
25-50-10
answer -35
Found 2 solutions by stanbon, edjones:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Correct
Cheers,
Stan H.

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
This illustrates a very important and often-times overlooked rule in squaring numbers.
-5*-5=25 but -5%5E2=-25 Check it out on a calculator. Make sure you don't use any brackets. It turns out -5%5E3 and -5%5E4 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.%28-5%29%5E2=25
Back to your problem:
-5%5E2%2B%2810%2A-5%29-10=-85
Ed Jones