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`A=(2x+3b)^2-12ab`

`=4x^2+12ab+9b^2-1ab`

`=4x^2+9b^2`

`B=(x+y)^2-(x-y)^2`

`=[x+y-(x-y)](x+y+x-y)`

`=(x+y-x+y)(x+y+x-y)`

 `=2y.2x`

`C=(3x-1)^2+(x+3)(2x-1)`

`=9x^2-6x+1+2x^2-x+6x-3`

`=7x^2-x-2`

`D=(2x-y)^2-(2x-y)(2x+y)`

`=(2x-y).(2x-y)-(2x-y)(2x+y)`

`=(2x-y)[2x-y-(2x+y)]`

`=(2x-y)(2x-y-2x-y)`

`=(2x-y).(-2y).`