Question

Urgent!
a) Daca 9x-5y supra 2x+3y=2 supra 21,atunci calculate valoarea raportului r=8x-3y supra 5x+9y

b) Aflati numerele naturale a,b,c care verifica relatiile:

a+b supra 9=b+c supra 12=c+a supra 11 si a+bc supra a(b+c)=109 supra 144

Answer 1

$\frac{9x-5y}{2x+3y} = \frac{2}{21}$

(9x-5y)*21=(2x+3y)*2
189x-105y=4x+6y
189x-4x=105y+6y
185x=111y       se imparte la 37 
5x=3y  => => x=3 si y=5
Verificam:
 $\frac{9*3-5*5}{2*3+3*5} = \frac{2}{21}$  ok

=>$\frac{8x-3y}{5x+9y} = \frac{8*3-3*5}{5*3+9*5}= \frac{24-15}{15+45} = \frac{9}{60} = \frac{3}{20}$