1,(X/2+Y)^2+(X/2-Y)^2
=X^2/4+XY+Y^2+X^2/4-XY+Y^2
=X^2/2+2Y^2
2,(M+N-P)(M-N+P)
=[M+(N-P)][M-(N-P)]
=M^2-(N-P)^2
=M^2-N^2+2PN-P^2
3,(7A-B-1)(7A+B-1)
=[(7A-1)-B][(7A-1)+B]
=(7A-1)^2-B^2
=49A^2-14A+1-B^2
4,(3A)^3*B^2/(8A^3B^2)
=27A^3B^2 /(8A^3B^2)
=27/8