`#tnvt`
`a)(5x-1)^2+2(1-5x)(4+5x)+(5x+4)^2`(sửa)
`=(5x-1)^2-2(5x-1)(4+5x)+(4+5x)^2`
`=(5x-1-4-5x)^2`
`=(-5)^2`
`=25`
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`(5x-1)^3+2(1-5x)(4+5x)+(5x+4)^2`
`=(5x-1)[(5x-1)^2+2(4+5x)]+(5x+4)^2`
`=(5x-1)(25x^2-10x+1+8+10x)+(25x^2+40x+16)`
`=(5x-1)(25x^2+9)+25^2+40x+16`
`=125x^3+45x-25x^2-9+45x^2+40x+16`
`=125x^3+95x+7`
