Question

Nr. naturale x , y, z sunt direct proportionale cu 3 , 4 ,5. Aflati nr. stiind ca x+2y+3z =78

Answer 1

x=3k
y=4k
z=5k
x+2y+3z=78
3k+2*4k+3*5k=78
3k+8k+15k=78
26k=78
k=78/26
k=3
x=3*3=9
y=4*3=12
z=5*3=15
Verificare:
9+2*12+3*15=9+24+45=69+9=78

Answer 2

(x;y;z) d.p.(3;4;5)
x+2y+3z=78
x/3=y/4=z/5=K }⇒x=3K
                           y=4K
                           z=5K
3K+2x4K+3x5K=78
3K+8K+15K=78
26K=78
K=78:26
K=3
x=3x3⇒x=9
y=3x4⇒y=12
z=3x5⇒z=15
Verificare: 9+2x12+3x15=9+24+45=78