`a)(x+1)²`
`=x²+2.x.1+1²`
`=x²+2x+1`
Áp dụng HĐT:`(A+B)²=A²+2AB+B`
`b)(x-2)²`
`=x²-2.x.2+2²`
`=x²-4x+4`
Áp dụng HĐT:`(A-B)²=A²-2AB+B`
`c)(x+3)²`
`=x²+2.x.3+3²`
`=x²+6x+9`
Áp dụng HĐT:`(A+B)²=A²+2AB+B`
`d)(x-4)²`
`=x²-2.x.4+4²`
`=x²-8x+16`
Áp dụng HĐT:`(A-B)²=A²-2AB+B`
`e)(5+x)²`
`=5²+2.5.x+x²`
`=25+10x+x²`
Áp dụng HĐT:`(A+B)²=A²+2AB+B`
`f)(6-x)²`
`=6²-2.6.x+x²`
`=36-12x+x²`
Áp dụng HĐT:`(A-B)²=A²-2AB+B`
`g)(2x+9)²`
`=(2x)²+2.2x.9+9²`
`=4x²+36x+81`
Áp dụng HĐT:`(A+B)²=A²+2AB+B`
`h)(4x-1/2)^2`
`=(4x)²-2.4x. 1/2+(1/2)^2`
`=16x²-4x+1/4`
Áp dụng HĐT:`(A-B)²=A²-2AB+B`
`i)(3x+2y)²`
`=(3x)²+2.3x.2y+(2y)²`
`=9x²+12xy+4y²`
Áp dụng HĐT:`(A+B)²=A²+2AB+B`
`j)(5xy-1)²`
`=(5xy)²-2.5xy.1+1²`
`=25x²y²-10xy+1`
Áp dụng HĐT:`(A-B)²=A²-2AB+B`