`#tnvt`
`4)\frac{x^2-y^2}{x^2y}.\frac{xy^2}{2x+2y}`
`=\frac{(x-y)(x+y)}{xy.x}.\frac{xy.y}{2(x+y)}`
`=\frac{x-y}{x}.\frac{y}{2}`
`=\frac{xy-y^2}{2x}`
`5)\frac{3x^2y-6xy^2}{3x^3-6x^2+3x}.\frac{x^2-1}{2x-4y}`
`=\frac{3x(xy-2y^2)}{3x(x^2-2x+1)}.\frac{(x-1)(x+1)}{2(x-2y)}`
`=\frac{y(x-2y)}{(x-1)^2}.\frac{(x-1)(x+1)}{2(x-2y)}`
`=\frac{y}{x-1}.\frac{x+1}{2}`
`=\frac{yx+y}{2x-2}`
`6)\frac{9x^3-25x}{x^2+x+1}.\frac{x^3-1}{3x^2-5x}`
`=\frac{x(9x^2-25)}{x^2+x+1}.\frac{(x-1)(x^2+x+1)}{x(3x-5)}`
`=\frac{(3x-5)(3x+5)}{1}\frac{x-1}{3x-5}`
`=\frac{3x+5}{1}.\frac{x-1}{1}`
`=(3x+5)(x-1)`
`=3x^2-3x+5x-5`
`=3x^2+2x-5`
