Răspunsuri

2014-08-19T16:28:10+03:00
L- lungimea, l-latimea
L=3l+30dam
P=140 dam => P=2L+2l
2(3l+30)+2l=140
6l+60+2l=140
8l=140-60
8l= 80
l=80/8=10 dam
L=3*10+30=30+30=60 dam
A= L*l = 10dam*60dam=600 dam²
2014-08-20T00:13:48+03:00
Notam cu x=latimea
notam cu 3x+30 lungimea

suma-=  \frac{perimetru'}{2} = \frac{140}{2} =70

x+3x+30=70
4x+30=70
4x=70-30
4x=40
x=10-latimea
10x3+30=60 lungimea