(1)
同时扩大10倍
2*10a/(10a+10b)
=20a/10(a+b)
=2a/(a+b)
(2)
a²/(a-b)-b²/(a-b)
=(a^2-b^2)/(a-b)
=(a+b)(a-b)/(a-b)
=a+b
(3)
2a/(a+b)=2*2a/(2a+4b)
1/(a+b)=1/(a+2b)
a+b=a+2b
b=2b
b=0
a≠0
(1)
同时扩大10倍
2*10a/(10a+10b)
=20a/10(a+b)
=2a/(a+b)
(2)
a²/(a-b)-b²/(a-b)
=(a^2-b^2)/(a-b)
=(a+b)(a-b)/(a-b)
=a+b
(3)
2a/(a+b)=2*2a/(2a+4b)
1/(a+b)=1/(a+2b)
a+b=a+2b
b=2b
b=0
a≠0