Question

Numerele a si b sunt directproportionale cu 4 si 5. Stiind ca suma lor este egala cu 18, determinati cele doua numere

Answer 1

a/4=b/5 ⇒5a-4b=0

5a-4b=0
a+b=18 | ·4

5a-4b=0
4a+4b=72
 Le adunam si obtinem :
9a=72⇒ a=8 b=10

Answer 2

[tex] \frac{a}{4} = \frac{b}{5} = \frac{a+b}{4+5} = \frac{18}{9}=2=>\\ \frac{a}{4}=2=>a=8\\ \frac{b}{5} =2=>b=10 [/tex]