Помогите сократить дробь

Question

Помогите сократить дробь

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Answer 1

(x^2 -10xy +25y^2 -1)/( (1-x+5y)(x+5y+1) )= ( (x-5y)^2 - 1 ) /( (1-x+5y)(x+5y+1) ) =
=( -(-x+5y+1)(x-5y+1) )/( (1-x+5y)(x+5y+1) )=  -(x-5y+1) / (x+5y+1) = (-x+5y-1)/(x+5y+1)