Question

帮忙算一道数学题2（x-2y）2-4（2y-x）+（x-2y）2-3（x-2y） 其中x=-1 y=1/2

Answer 1

2(x-2y)²-4(2y-x)+(x-2y)²-3(x-2y)
=2(x-2y)²+4(x-2y)+(x-2y)²-3(x-2y)
=3(x-2y)²+(x-2y)
=(x-2y)(3x-6y+1)
=(-1-1)*(-6+1)
=10

Answer 2

2(x-2y)^2-4(2y-x)+(x-2y)^2-3(x-2y)
=(x-2y)[2(x-2y)+4+(x-2y)-3)
=(x-2y)[3x-6y+1]
原式=(-1-1)[-3-3+1]
=(-2)*(-5)
=10

或令(x-2y)=t
原式=2t²+4t+t²-3t
=3t^2+t
t=-1-1=-2
原式=3*（-2）²-2=12-2=10

Answer 3

(x-2y)=(-1-1)=-2

2(x-2y)^2-4(2y-x)+(x-2y)^2-3(x-2y)

=3(x-2y)^2+(x-2y)

=3*4-2=10

Answer 4

=2(x-2y)-4(2y-x)+(x-2y)²-3(x-2y)
=2(x-2y)+4(x-2y)+(x-2y)²-3(x-2y)
=3(x-2y)+(x-2y)²

其中x=-1 y=1/2

所以：
(x-2y)(3+x-2y)
=(-1-1)(3-1-1)
=(-2)*1
=-2