Question

Calculați 27% din 81(și rezolvarea)
Dacă 2x+5y/x+y=4,5 află: x+y

Answer 1

a. 27/100 ·81=27·81/100=2187/100=21,87;
b. 2x+5/x+y=4,5
⇒2x+5/x+y=45/10⇒45[x+y]=10[2x+5]
⇒45x+45y=20x+50
⇒45x-20x=50-45y[se elimina y];
⇒25x=50-45⇒25x=5⇒x=5/25=1/5⇒x=1/5;
⇒50-45y=5⇒45y=45⇒y=1;
⇒x+y=1/5+1=1/5+5/5=6/5⇒x+y=6/5;