Có gì sai sót mong được chỉ bảo ạ:
`d)(2x+1)^2+2.(2x+1).(3-2x)+(3-2x)^2`
`=(2x+1+3-2x)^2`
`=4^2=16.`
`e)(4-x).(x+4).(x^2+16)-(x^2+5)^2`
`=(4-x).(4+x).(x^2+16)-(x^2+5)^2`
`=(4^2-x^2).(x^2+16)-(x^2+5)^2`
`=(16-x^2).(x^2+16)-(x^2+5)^2`
`=-(-16+x^2).(x^2+16)-(x^2+5)^2`
`=-(x^2-16).(x^2+16)-(x^2+5)^2`
`=-[(x^2)^2 - 16^2]-[(x^2)^2+2.x^2 .5+5^2]`
`=-(x^4-256)-(x^4+10x^2+25)`
`=-x^4+256-x^4-10x^2-25`
`=-2x^4-10x^2+231.`
