1. Feb 25, 2010

DaleSwanson

So I just got back from my math class, we were going over exponents. Right before we left he gave us a problem and we turned it in, I was just wondering if I got it right.

Simplify:
(54-3y)3 * (5y-2)2

I got:
512-9y3 * 5y2-4

5-9y3+y2+8

I applied the powers to the parenthesis, then added the two exponents. The addition of the exponents is here:
http://www.wolframalpha.com/input/?i=%2812-9y^3%29+%2B+%28y^2+-+4%29

However when I just pop the original problem into wolfram alpha I get:
http://www.wolframalpha.com/input/?i=%28%285^%284-3y%29%29^3%29+*+%28%285^%28y-2%29%29^2%29
58-7y

So I guess I have two questions. First is my answer right? Second how did Wolfram come up with that answer?

2. Feb 25, 2010

VeeEight

You are applying the exponentiation rules incorrectly in your first step - perhaps you want to review it. When you bring down the 3, you multiply it to the (4-3y) to get (12-9y) instead of taking powers. Do the same for the other term. Then you can reduce the exponents.

See rules 3 here: http://mathworld.wolfram.com/ExponentLaws.html

3. Feb 25, 2010

DaleSwanson

Thanks. Stupid mistake, always the stupid mistakes.

4. Feb 25, 2010

VeeEight

That's fine - when you make mistakes you go back and look at the definitions, problems, and learn a lot that way. Cheers