a b=2 ab=4分之3 则a-b=()

因为ab≠0,且a分之一+b分之一=4,所以a+b=4ab,-3a-3b=-12ab,4a+4b=16ab所以(-3a+2ab-3b)分之(4a+3ab+4b)=-19ab/10ab=-19/10

答案是4先通分,分子变成a^2-b^2,分母是（（根号ab)+b）（a-根号ab）分母前面提出根号b,后面提出根号a,分子写成（a+b）（a-b）,分母变成根号下ab乘以(a-b)谢啦再问：（分母前面

a分之1-b分之1=5sob-a=5absoa-b=-5ab2a+3ab-2b2(a-b)+3ab-10ab+3ab----------------=---------------=---------

a分之1-b分之1=3b-a=3ab-3a+2ab+3b分之-4a+3ab+4b=[4(b-a)+3ab]/[3(b-a)+2ab]=15ab/11ab=15/11

由b/a+a/b=2,(a^2+b^2)/(ab)=2,a^2+b^2=2ab,(a^2+ab+b^2)/(a^2+4ab+b^2)=(2ab+ab)/(2ab+4ab)=3ab/(6ab)=1/2再

(a²-ab+b²)/(a²+2ab+2b²)分子分母同除以b²a²/b²=(a/b)²=9/16ab/b²=

因为：a+b=4ab所以：（2a-ab+2b)/(2ab)=[2(a+b)-ab]/(2ab)=(2×4ab-ab)/(2ab)=(8ab-ab)/(2ab)=7/2

由a分之1减b分之1=4,可知（b-a）/(ab)=4,设b-a=4k,则ab=k,期中k不得02a-2b+7ab分之a-2ab-b=2（a-b）+7ab分之（a-b）-2ab=-4k-2k分之-8K

a-b=4ab所以原式=[2(a-b)+7ab]分之[(a-b)-2ab]=[2(4ab)+7ab]分之[(4ab)-2ab]=15ab分之2ab=15分之2

ab+2ab+ab=ab(a+2ab+b)∵a+b=2/3,ab=2,∴原式=2×(2/3+2×2)=28/3爱执着

ab/(2a-b)=2则(2a-b)/ab=1/23ab/(2a-b)+2[2a-b]/ab=3[ab/(2a-b)]+2[(2a-b)/ab]=3×2+2×1/2=6+1=7

a分之1+b分之1=5,通分得a+b=5ab2a+2b-7ab=10ab-7ab=3aba-3ab+b=5ab-3ab=2ab所以结果得2/3

2a-2b+7ab分之a-2ab-b=（a-2ab-b）/(2a-2b+7ab)分子分母同时除以abab都不为0=(1/b-2-1/a)/(2/b-2/a+7)=(-2-(1/a-1/b))/(7-2

1/a+1/b=(b+a)/ab=2/3

2a+2b-ab分之a+b+2ab=2(a+b)-ab分之a+b+2ab=6ab-ab分之3ab+2ab=5ab分之5ab=1

1/A+1/B=3(A+B)/(AB)=3A+B=3ABA-3AB+B=3AB-3AB=0整个式子=0

1/a+1/b=4a+b=4ab(a+b-3ab)/(2a+2b-7ab)=(4ab-3ab)/(2*4ab-7ab)=ab/(ab)=1

a分之1＋b分之1=4a+b=4ab分式-3a+2ab-3b分之4a+3ab+4b=(4(a+b)+3ab)/(-3(a+b)+2ab)=(4*4ab+3ab)/(-3*4ab+2ab)=19ab/(

1/a-1/b=4(a-2ab-b)/(2a-2b+7ab)=(1/b-2-1/a)/[2(1/b-1/a)+7]=(-4-2)/(-4+7)=-6/3=-2

1/a-1/b=(b-a)/ab=1推出b-a=ab故a-2ab-b=ab-2ab=-ab2a+3ab-2b=2ab+3ab=5ab原式=-ab/5ab=-1/5