Question 65375
4r^2 - 25s^2
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2r^2 + 3rs - 20s^2 

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Factor where you can, as follows:
[(2r-5s)(2r+5s)]/[2r-5s)(r+4s)]
Cancel the factor that is common to the numerator and denominator:
=[2r+5s]/[r+4s]
Cheers,
Stan H.