=x2+2x4+3x6+⋯+1005x20102x+4x3+6x5+⋯+2010x2009
Factor x out of all the terms in the numerator and factor 2 out of all the terms in the denominator to get:
=x(x+2x3+3x5+⋯+1005x2009)2(x+2x3+3x5+⋯+1005x2009)
Now we can cancel out the common factor from the numerator and denominator to get:
=x2
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