Pdreptunghi=2L+2l⇔2L+2l=108
l=L:2
[tex]2L+ 2*\frac{L}{2} =108 \\ 2L+ \frac{2L}{2} =108 \\ \text{Amplificam 2L si 108 cu 2 pentru a obtine numitor comun} \\ \frac{4L}{2} + \frac{2L}{2} = \frac{216}{2} /*2 \\ 4L+2L=216 \\ 6L=216/:6 \to L=36 [/tex]
[tex]l= \frac{L}{2} = \frac{36}{2} =18 [/tex]
