Question

有一题代数式，先化简,再求值的

题目是x²+(2xy-3y²)-2(x²+xy-2y²),其中x=-1,y=3，大家帮忙算算啊，我算不出来呜

Answer 1

(x+3y)(x-y)-2{(x+2y)(x-y)}=(x-y){(x+3y)-2(x+2y)}=-(x-y)(x+y)=-(x*-y*)=y*-x*
代入得：3*-1*=9-1=8
其中*代表2哈 平方哥不会打的
望采纳

Answer 2

x²+(2xy-3y²)-2(x²+xy-2y²),
=x²+2xy-3y²-2x²-2xy+4y²
=x²-2x²+2xy-2xy-3y²+4y²
=-x²-7y²
当x=-1.y=3时
-x²-7y²
=-(-1)²-7x3²
=1²-63
=-62

Answer 3

x²+(2xy-3y²)-2(x²+xy-2y²)
=x²+2xy-3y²-2x²-2xy+4y²
=y²-x²
=3²-（-1）²
=9-1
=8

Answer 4

=X²+y²-2x²
结果是8

Answer 5

等于8