`(2x^2+x)^2-4(2x^2+x)+3`
`=4x^4+4x^3+x^2-8x^2-4x+3`
`=4x^4+4x^3-7x^2-4x+3`
`=4x^4+4x^3-7x^2-7x+3x+3`
`=4x^3(x+1)-7x(x+1)+3(x+1)`
`=(x+1)(4x^3-7x+3)`
`=(x+1)(4x^3-4x-3x+3)`
`=(x+1)[4x(x^2-1)-3(x-1)]`
`=(x+1)[4x(x-1)(x+1)-3(x-1)]`
`=(x+1)(x-1)(4x^2+4x-3)`
`=(x+1)(x-1)(4x^2+6x-2x-3)`
`=(x+1)(x-1)[2x(2x+3)-(2x+3)]`
`=(x+1)(x-1)(2x-1)(2x+3)`