`10x(x-y) - 8y(y-x)`
`= 10x(x-y) + 8y(x-y)`
`= (10x+8y)(x-y)`
`= 2(5x+4y)(x-y)`
\(10x\left(x-y\right)-8y\left(y-x\right)\)
\(=10x\cdot\left(x-y\right)-8y\cdot-\left(x-y\right)\)
\(=10x\left(x-y\right)+8y\left(x-y\right)\)
\(=\left(10x+8y\right)\left(x-y\right)\)
\(=\left(2\cdot5x+2\cdot4y\right)\left(x-y\right)\)
\(=2\left(5x+4y\right)\left(x-y\right)\)