Question

Determinati numerele x si Y stiind ca sunt invers proportionale cu 2 si 5 iar suma lor este 7

Answer 1

{x,y) i.p. {2,5}
x+y=7
x=
$\frac{1}{2} k \\ y= \frac{1}{5}*k \\ \frac{1}{2}k+ \frac{1}{5}k=7 \\ \frac{7}{10}k=7 \\ k=10\\ x= \frac{1}{2}*10 = 5 \\ y= \frac{1}{5}*10=2$

Answer 2

{x;y} <---> {2;5} ; <---> = invers proportonial
x+y=7
x/(1/2)=y/(1/5)=k
2x=k=>x=k/2
5y=k=>y=k/5
x+y=7 => k/2+k/5=7 aducem la acelasi numitor ( 10 daca nu stiai)
5k+2k=70
7k=70
k=10
x=k/2=>x=5
y=k/5=>y=2