Question

Dacă numerele x şi y sunt direct proporţionale cu 5 şi 7, calculaţi 3x +4y supra 5y- 2x

Answer 1

x=5k
y=7k

(3x+4y)/(5y-2x)=
(15k+28k)/(35k-10k)= 43k/25k=43/25

Answer 2

x/5=y/7=k
⇒x/5=k⇒x=5k;
⇒y/7=k⇒y=7k;
⇒3x+4y/5y-2x
⇒3·5k+4·7k/5·7k-2·5k
⇒15k+28k/35k-10k
⇒43k/25k⇒se reduce k cu k;
⇒43/25;