`9)`
`4x^2-36xy+56y^2`
`=4x^2-28xy-8xy+56y^2`
`=(4x^2-28xy)-(8xy-56y^2)`
`=4x(x-7y)-8y(x-7y)`
`=(x-7y)(4x-8y)`
`=4(x-7y)(x-2y)`
`10)`
`3x^2-5xy+2y^2`
`=3x^2-3xy-2xy+2y^2`
`=(3x^2-3xy)-(2xy-2y^2)`
`=3x(x-y)-2y(x-y)`
`=(x-y)(3x-2y)`
`11)`
`-2x^2+7xy-5y^2`
`=-2x^2+2xy+5xy-5y^2`
`=-(2x^2-2xy)+(5xy-5y^2)`
`=-2x(x-y)+5y(x-y)`
`=(x-y)(-2x+5y)`
`12)`
`3x^2+7xy-10y^2`
`=3x^2-3xy+10xy-10y^2`
`=3x(x-y)+10y(x-y)`
`=(x-y)(3x+10y)`
`13)`
`-2x^2+5xy-3y^2`
`=-2x^2+2xy+3xy-3y^2`
`=-(2x^2-2xy)+(3xy-3y^2)`
`=-2x(x-y)+3y(x-y)`
`=(x-y)(-2x+3y)`
`14)`
`-8x^2+xy+7y^2`
`=-8x^2+8xy-7xy+7y^2`
`=-(8x^2-8xy)-(7xy-7y^2)`
`=-8x(x-y)-7y(x-y)`
`=(x-y)(-8x-7y)`
`15)`
`-3x^2-5xy+8y^2`
`=-3x^2+3xy-8xy+8y^2`
`=-(3x^2-3xy)-(8xy-8y^2)`
`=-3x(x-y)-8y(x-y)`
`=(x-y)(-3x-8y)`
`=(y-x)(3x+8y)`
