Question

a) Daca 5a=6b, calculati a supra b 

 

b) Daca a+b=1 si 2a supra 5=3b supra 7, aflati nr a si b      

 

 

 

Dau multe puncte

Answer 1

a) 5a=6b ⇒ a/b=6/5;
a+b=1 ⇒ a=1-b; 2a/5=3b/7 ⇒ 2(1-b)/5=3b/7 ⇒ 14-14b=15b ⇒ 29b=14 ⇒ b=14/29 ⇒ 
a=15/29

Answer 2

$\dfrac{2a}{5}=\dfrac{3b}{7}\Leftrightarrow\dfrac{a}{15}=\dfrac{b}{14}=\dfrac{a+b}{14+15}=\dfrac{1}{29}\Rightarrow a=\dfrac{15}{29};\ b=\dfrac{14}{29}$