Răspuns :
a/b = 2/5 ==> b = 5a/2
a/(a+b) = a/(a+5a/2) =
= a/(2a/2 +5a/2) =
= a/7a/2 =
= 2a/7a =
= 2/7
a/(a+b) = a/(a+5a/2) =
= a/(2a/2 +5a/2) =
= a/7a/2 =
= 2a/7a =
= 2/7
[tex]\dfrac{a}{b}[/tex]=[tex]\dfrac{2}{5}[/tex]=k
a=2k
b=5k
[tex]\dfrac{a}{a+b}[/tex]=[tex]\dfrac{2k}{2k+5k}[/tex]=[tex]\dfrac{2k}{7k}[/tex]=[tex]\dfrac{2}{7}[/tex]