`a,(x+7)^2=x^2+2.x.7+7^2=x^2+14x+49`
`b,(6x+10)^2=(6x)^2+2.6x.10+10^2=36x^2+120x+100`
`c,(1/4x+2/3)^2=(1/4x)^2+2.(1)/4x.(2)/3+(2/3)^2=1/16x^2+1/3x+4/9`
`d,(x-8)^2=x^2-2.x.8+8^2=x^2-16x+64`
`e,(3x-9)^2=(3x)^2-2.3x.9+9^2=9x^2-54x+81`
`f,(1/5x-5/3)^2=(1/5x)^2-2.(1)/5x.(5)/3+(5/3)^2=1/25x^2-2/3x+25/9`