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Algebra Difficulty 1.9 Junior Find the answer

Simplify the expression 20(x+y)19(y+x)20(x+y)-19(y+x) for all values of xx and yy.

A number or a short expression. Spacing and $ signs are ignored.

Solution

Simplifying, we see that 20(x+y)19(y+x)=20x+20y19y19x=x+y20(x+y)-19(y+x)=20x+20y-19y-19x=x+y for all values of xx and yy.

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