当x=2,y=1÷2时,化简代数式(x+y)(x-y)+(x-y)²-(x²-3xy)的值

当x=2,y=1÷2时,化简代数式(x+y)(x-y)+(x-y)²-(x²-3xy)的值
当x=2,y=1÷2时,化简代数式(x+y)(x-y)+(x-y)²-(x²-3xy)的值

当x=2,y=1÷2时,化简代数式(x+y)(x-y)+(x-y)²-(x²-3xy)的值
原式=（X+Y+X-Y)(X-Y)-X(X-3Y)=X(2X-2Y-X+3Y)=x²+XY=5

(x+y)(x-y)+(x-y)²-(x²-3xy)
=x²-y²+x²-2xy+y²-x²+3xy
=x²+xy
=x(x+y) 把x=2,y=1/2代入
=2(2+1/2)=5