1.先化简,再求值：x²-64y²分之2x-x-8y分之1其中x=1y=-¼2.解方程1-x+1分之x-1=x-2分之33.已知m,n满足n=4+2m,求{（m²+n²)-(m-n)²+2n(m-n)}÷4n的值4.化简求值：x(x+1)-3(x²-x)+3x(x-

Question

1.先化简,再求值：x²-64y²分之2x - x-8y分之1 其中x=1 y= -¼
2.解方程 1 - x+1分之x-1=x-2分之3
3.已知m,n满足n=4+2m,求{（m²+n²) - (m-n)²+2n(m-n)}÷4n 的值
4.化简求值：x(x+1) - 3(x²-x)+3x(x-2),其中x= -1

Answer 1

3、
{（m²+n²) - (m-n)²+2n(m-n)}÷4n
=【2mn+2nm-2nn】/4n
=（2m-n）/2
=[ 2m - (4+2m)] /2
=-2
4、
x(x+1) - 3(x²-x)+3x(x-2)
=x(x+1) - 3x(x-1)+3x(x-2)
=x(x+1)+ 3x( x-2 -x+1)
=x(x+1)-3x
=x(x+1-3)
=x(x-2)
=3
1和2题看不出你问题的优先级.按我理解的解答吧：
1、
2x /（x²-64y²） - 1/(x-8y)
=2x/[(x-8y)(x+8y)] - 1/(x-8y)
=[2x - (x+8y) ] / [(x+8y)(x-8y)]
=(x-8y)/ [(x+8y)(x-8y)]
=1/(x+8y)
=-1
2、
1 - （x-1）/ (x+1) = 3/ (x-2)
2/(x+1)= 3/(x-2)
3(x+1) = 2(x-2)
x = -7