x^2y^2-4xy-20y-25y^2
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x²y²-4xy-20y-25y²= x²y²-25y²-4xy-20y= y²(x²-5²)-4y(x+5)= y²(x-5)(x+5)-4y(x+5) = (x+5)(y²(x-5)-4y)=(x+5)(xy²-5y²-4y)