g) `x^2+7xy+10y^2`
`=x^2+2xy+5xy+10y^2`
`=x(x+2y)+5y(x+2y)`
`=(x+2y)(x+5y)`
h) `x^2-6xy+5y^2`
`=x^2-xy-5xy+5y^2`
`=x(x-y)-5y(x-y)`
`=(x-y)(x-5y)`
i) Sửa đề: `a^2-7ab+12b^2`
`=a^2-3ab-4ab+12b^2`
`=a(a-3b)-4b(a-3b)`
`=(a-3b)(a-4b)`
j) `x^2-x-6`
`=x^2+2x-3x-6`
`=x(x+2)-3(x+2)`
`=(x+2)(x-3)`
l) `x^3-19x-30`
`=x^3+2x^2-2x^2-4x-15x-30`
`=x^2(x+2)-2x(x+2)-15(x+2)`
`=(x+2)(x^2-2x-15)`
`=(x+2)(x+3x-5x-15)`
`=(x+2)[x(x+3)-5(x+3)]`
`=(x+2)(x+3)(x-5)`