Question

упростите пожалуйста нижнее

Answer 1

$\displaystyle\tt \ \ \ \frac{4x^2-81y^2-4x+1}{2x+9y-1}+7y= \frac{(4x^2-4x+1)-81y^2}{2x+9y-1}+7y=\\\\\\ =\frac{(2x-1)^2-(9y)^2}{2x+9y-1}+7y=\frac{(2x-1-9y)(2x-1+9y)}{2x+9y-1}+7y=\\\\\\=2x-1-9y+7y=2x-2y-1$