初中数学问题,分式.化简.

1.化简:({x+1}分之一+{1-x的平方}分之1)÷{x+1}分之3x

=[(1-x)/(1-x^2)+1/(1-x^2)](x+1)/3x
=(2-x)/(1+x)(1-x)×(x+1)/3x
=(2-x)/3x(1-x)

2:{x的平方-16}分之{6-5x+x的平方}÷{4-x}分之{x-3}乘以{4-x的平方} 分之{x的平方+5x+4}
=(x-2)(x-3)/(x+4)(x-4)×(4-x/(x-3)×(x+1)(x+4)/(2+x)(2-x)
=(x+1)/(x+2)

3,(根号二-1)a=1,∴a=1+√2

1加a分之1}再分之1 - 1加a分之1 =a/(a+1)-1/(a+1)
=(a-1)/(a+1)
=√2-1

4,.[a+(a-1-a分之1)乘以{a的平方-a+1分之2-a-a的平方}]÷(a-2)(a+1)

=[a+(a^2-a-1)/a×(-a^2-a+2)/(a^2-a+1)]×1/(a-2)(a+1)
=[a-a-2]×1/(a-2)(a+1)
=-2/(a-2)(a+1)