Răspunsuri

2014-10-31T18:08:19+02:00
P=2(L+l)
2(L+l)=42
L+l=42:2=21
l=40/100.L=2L/5
2L/5+L=21
2L+5L=21.5
7L=21.5
L=15 cm
l=2.15/5=6 cm
A=L.l=15.6=90 cm ²