几道初二数学题，高手进

显示全部楼层 · 2011-3-4 18:40:34

(1)1/a-1/b=3
(2a＋3ab－2b)/(a－2ab－b)=ab(2/b+3-2/a)/ab(1/b-2-1/a)=(2/b+3-2/a)/(1/b-2-1/a)=(2/a-2/b-3)/(1/a-1/b+2)=[2(1/a-1/b)-3]/[(1/a-1/b)+2]=(2X3-3)/(3+2)=3/5=0.6(2)（ 3x/(x－1)－x/(x＋1) )×(x2－1)/x ={[3x(x+1)-x(x-1)]/(x2－1)}×(x2－1)/x=3(x+1)-(x-1)=3x+3-x-1=2x+2=2(√2-2)+2=2√2-4+2=...

千问 · 2011-3-4 18:40:34

(1) 1/a－1/b=3推得b-a=3ab
(2a＋3ab－2b)/(a－2ab－b)=(-6ab+3ab)/(-3ab-2ab)=3/5(2)(3x/(x－1)－x/(x＋1) )×(x2－1)/x=[3x(x+1)-x(x-1)]/x=3x+3-x+1=2x+4=2√2(3)((x－2)/(x...

千问 · 2011-3-4 18:40:34

1
1/a-1/b=3.两边同乘ab得b-a=3ab则a-b=-3ab(2a+3ab-2b)/(a+2ab-b)原式=2(a-b)+3ab/(a-b)+2ab
把a-b=-3ab代入得-6ab+3ab/-3ab+2ab=-3/-1=32=[3x(x+1)-x(x-1)/(x-1)...

千问 · 2011-3-4 18:40:34

1/a-1/b=(b-a)/ab=3即b-a=3ab(2a+3ab-2b)/(a-2ab-b)=(3ab-6ab)/(-3ab-2ab)=3/5第二题：原式=[2x(x+2)/(x-1)(x+1)]×(x+1)(x-1)/x=2(x+2)=2倍根号第三题：化解后，原式=x2-3x+4...