\(a,=\dfrac{\left(x-y\right)\left(x+y\right)}{5\left(x-y\right)}=\dfrac{x+y}{5}\\ b,=\left(4x+5-x-5\right)^2=\left(3x\right)^2=9x^2\\ c,=\left(x-3\right)\cdot\dfrac{4x-12-3x-9+18}{2\left(x-3\right)\left(x+3\right)}=\dfrac{x-3}{2\left(x-3\right)}=\dfrac{1}{2}\)
Ủa tính ra mjk ngu toán tự nhiên đi bấm vào toán chi trời=))
a/ \(\dfrac{x^2-y^2}{5x-5y}=\dfrac{\left(x-y\right)\left(x+y\right)}{5\left(x-y\right)}=\dfrac{x+y}{5}\)
b/ \(\left(4x+5\right)^2-2\left(4x-5\right)\left(x+5\right)+\left(x+5\right)^2\)
\(=\left(4x+5-x-5\right)^2=9x^2\)
c/ \(\left(x-3\right)\left(\dfrac{2}{x+3}-\dfrac{3}{2x-6}+\dfrac{9}{x^2-9}\right)\)
\(=\left(x-3\right)\left(\dfrac{2.2\left(x-3\right)-3\left(x+3\right)+9.3}{2\left(x^2-9\right)}\right)\)
\(=\left(x-3\right)\left(\dfrac{x+6}{2\left(x+3\right)\left(x-3\right)}\right)\)
\(=\dfrac{\left(x-3\right)\left(x+6\right)}{2\left(x+3\right)\left(x-3\right)}\)
\(=\dfrac{x+6}{2x+6}\)
