当2x-y=3时 则 2(y - 2x)2 - 4(2x - y)2 - 6x + 3y=?

当2x-y=3时 则 2(y - 2x)2 - 4(2x - y)2 - 6x + 3y=?
当2x-y=3时 则 2(y - 2x)2 - 4(2x - y)2 - 6x + 3y=?

当2x-y=3时 则 2(y - 2x)2 - 4(2x - y)2 - 6x + 3y=?
2x-y=3
则y-2x=-3
则(y-2x)²=(2x-y)²=9
2(y - 2x)²- 4(2x - y)² - 6x + 3y
=2(2x - y)²-4(2x - y)²-3(2x-y)
=-2(2x - y)²-3(2x - y)
=-2×9-3×3
=-27

原式=x^4+x+x+1
=x(x³+1)+(x+1)
=x(x+1)(x²-x+1)+(x+1)
=(x+1)(x³-x²+x+1)
3（x-y）-2（x+y）+2
=3x-3y-2x-2y+2
=x-5y+2
=-2-5×3/4+2
=-15/4