`c) x^3-7x-6`
`=x^3-3x^2+3x^2-9x+2x-6`
`=x^2(x-3)+3x(x-3)+2(x-3)`
`=(x-3)(x^2+3x+2)`
`=(x-3)(x^2+x+2x+2)`
`=(x-3)[x(x+1)+2(x+1)]`
`=(x-3)(x+1)(x+2)`
`d) x^3+5x^2+8x+4`
`=x^3+x^2+4x^2+4x+4x+4`
`=x^2(x+1)+4x(x+1)+4(x+1)`
`=(x+1)(x^2+4x+4)`
`=(x+1)(x+2)^2`
`g) x^3+x^2-x+2`
`=x^3+2x^2-x^2-2x+x+2`
`=x^2(x+2)-x(x+2)+(x+2)`
`=(x+2)(x^2-x+1)`
`h) x^3-6x^2-x+30`
`=x^3+2x^2-8x^2-16x+15x+30`
`=x^2(x+2)-8x(x+2)+15(x+2)`
`=(x+2)(x^2-8x+15)`
`=(x+2)(x^2-5x-3x+15)`
`=(x+2)[x(x-5)-3(x-5)]`
`=(x+2)(x-5)(x-3)`
