SOLUTION: Find the product: (2x-7y)(2x+7y)

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Question 610655: Find the product: (2x-7y)(2x+7y)
Found 2 solutions by Maths68, ashipm01:
Answer by Maths68(1474) About Me  (Show Source):
You can put this solution on YOUR website!
%282x-7y%29%282x%2B7y%29
=2x%282x%2B7y%29-7y%282x%2B7y%29
=4x%5E2%2B14xy-14xy-49y%5E2%29
=4x%5E2%2Bcross%2814xy%29-cross%2814xy%29-49y%5E2%29
=4x%5E2-49y%5E2%29
OR
We know that
%28a%5E2-b%5E2%29=%28a-b%29%28a%2Bb%29
Therefore
%282x-7y%29%282x%2B7y%29=%28%282x%29%5E2-%287y%29%5E2%29
%282x-7y%29%282x%2B7y%29=%28%282x%29%5E2-%287y%29%5E2%29
%282x-7y%29%282x%2B7y%29=4x%5E2-49y%5E2%29

Answer by ashipm01(26) About Me  (Show Source):
You can put this solution on YOUR website!
To multiply those two polynomials, multiply each term in each polynomial by every term in every other polynomial. For this case, there are two polynomials and each of them has two terms, so the resulting expression will have four terms before simplification (2 polynomials * 2 terms / polynomial = 4 terms).
The original expression was
+%282x-7y%29%2A%282x%2B7y%29+
The first polynomial has the following two terms: +2x+ and +-7y+
And the second polynomial has the following two terms: +2x+ and +7y+
So you just need to multiply each term in the first polynomial by each term in the second polynomial and then sum the products. This results in the following term products:
+2x+%2A+2x+, +2x+%2A+7y+, +-7y+%2A+2x+, and +-7y+%2A+7y+
Performing the multiplications in each of the terms yields the following terms:
+4x%5E2+, +14xy+, +-14xy+, and +-49y%5E2+
Summing those terms results in the following expression:
+4x%5E2+%2B+14xy+%2B+-14xy+%2B+-49y%5E2+
Which simplifies to the answer:
+%282x-7y%29%2A%282x%2B7y%29+=+4x%5E2+-+49y%5E2+