1.当x≠0时,式子(x-1)(x+1)+1 / x的三次方+5x = x / x²+5成立
2.若|x-1| / (x-1)² = - 1/x-1 则x＜1
3.先化简再求值
2/ 4-4x+x² ÷ (x+3) * x-2 / x+3 其中x=2+根号2
=2/(2-x)²÷(x+3)×(x-2)/(x+3)
=2/(x-2)
=2/(2+√2-2)
=2/√2
=2√2/(√2)²
=√2第二题为什么是x<1？ 第三题2/(x-2)这一步怎么得来的‘’‘2/(4-4x+x²)=2/(2-x)²|x-1| / (x-1)² = - 1/x-1 则x＜1∵┃x-1┃=±(x-1)x＜0=-(x-1) x＞0 =x-1