Question

Stiind ca a supra b = 4 supra 3.
Dau 40 de pcte si COROANA
a+b supra 3a-b

Answer 1

a/b=4/3=k
a=4k si b=3k

a+b/3a-b = 4k+3k/3*4k - 3k = 7k/12k-3k = 7k/9k = 7/9

Answer 2

Alta metoda: aplicand proprietatile proportiilor derivate schimband in acelasi fel fiecare raport.
Daca a/b=4/3⇒(a+b)/b=(4+3)/3⇒a+b=7b/3 (1)  
Daca a/b=4/3⇒3a/b=(4·3)3⇒3a/b=4/1⇒(3a-b)/b=(4-1)/1⇒3a-b=3b (2)  
Din (1) si (2) prin impartire de relatii⇒(a+b)/(3a-b)=(7b/3):3b⇒  
(a+b)/(3a-b)=7/9