Question

先化简,再求值:(2x+y)(2x-y)+(x+y)的平方-2(2x的平方-xy),其中x=2,y=-四分之一

用乘法公示做，急，快

Answer 1

(2x+y)(2x-y)+(x+y)的平方-2(2x的平方-xy)
=(2x+y)(2x-y)+(x+y)²-2x(2x-y)
=(2x+y-2x)(2x-y)+(x+y)²
=y(2x-y)+(x+y)²
=2xy-y²+x²+2xy+y²
=x²+4xy
=4-4×2×1/4
=2

Answer 2

解答：

(2x+y)(2x-y)+(x+y)^2-2(2x^2-xy)=4x^2-y^2+x^2+2xy+y^2-4x^2+2xy
=x^2+4xy=2^2+4*2*(-1/4)=4-2=2

Answer 3

=4x2-y2+x2+2xy+y2-4x2+2xy
=x2+4xy
把x，y的值代入
=2

Answer 4

=4x2-y2+x2+ 2xy+y2-4x2+2xy=x2+4xy=2*2+4*2*(-1\4)=4-2=2

Answer 5

如图