SOLUTION: 4x^2-81

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Question 153260: 4x^2-81
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Do you want to factor this?



4x%5E2-81 Start with the given expression.


%282x%29%5E2-81 Rewrite 4x%5E2 as %282x%29%5E2.


%282x%29%5E2-%289%29%5E2 Rewrite 81 as %289%29%5E2.


Notice how we have a difference of squares. So let's use the difference of squares formula A%5E2-B%5E2=%28A%2BB%29%28A-B%29 to factor the expression:


%282x%2B9%29%282x-9%29 Factor the expression using the difference of squares.


So 4x%5E2-81 factors to %282x%2B9%29%282x-9%29.


In other words 4x%5E2-81=%282x%2B9%29%282x-9%29.