`2.`
`a)(xy+3)²`
`=(xy)²+2.xy.3+3²`
`=x²y²+6xy+9`
`b)(3-x)(3+x)`
`=3²-x²`
`=9-x²`
`c)(5-2x)²`
`=5²-2.5.2x+(2x)²`
`=25-20x+4x²`
`d)(5x-1)³`
`=(5x)³-3.(5x)².1+3.5x.1²-1³`
`=125x³-75x²+15x-1`
`e)(x+1/3)^3`
`=x³+3.x². 1/3+3.x. (1/3)^2+(1/3)^3`
`=x³+x²+1/3x+1/27`
`f)(2x-y)(4x²+2xy+y²)`
`=(2x-y)[(2x)²+2x.y+y²]`
`=(2x)³-y³`
`=8x³-y³`
`m)(x+3)(x²-3x+9)`
`=(x+3)(x²-x.3+3²)`
`=x³+3³`
`=x³+27`
`3.`
`a)(x+y)²+(x-y)²`
`=x²+2xy+y²+x²-2xy+y²`
`=(x²+x²)+(2xy-2xy)+(y²+y²)`
`=2x²+2y²`
`b)(x+3)³-x²(x+9)`
`=x³+3.x².3+3.x.3²+3³-x³-9x²`
`=x³+9x²+27x+27-x³-9x²`
`=(x³-x³)+(9x²-9x²)+27x+27`
`=27x+27`
`c)(2x+3y)²-2.(2x+3y).(2x+y)+(2x+y)²`
`=[(2x+3y)-(2x+y)]²`
`=(2x+3y-2x-y)²`
`=(2y)²`
`=4y²`
