х - длина участка
у - ширина участка
\left \{ {{x*y=720} \atop {x+y=54}} \right. => \left \{ {{x*y=720} \atop {x=54-y}} \right. => \left \{ {{(54-y)*y=720} \atop {x=54-y}} \right. => \left \{ {{54y-y^2-720=0} \atop {x=54-y}} \right. => \left \{ {{D=54^2-4*720=36} \atop {y_1=\frac{-54+6}{-2}=24;\ y_2=\frac{-54-6}{-2}=30}} \right. => \left \{ {{y_1=24;\ y_2=30} \atop {x_1=54-24=30;\ x_2=54-30=24}} \right." alt="\left \{ {{x*y=720} \atop {2x+2y=108}} \right. => \left \{ {{x*y=720} \atop {x+y=54}} \right. => \left \{ {{x*y=720} \atop {x=54-y}} \right. => \left \{ {{(54-y)*y=720} \atop {x=54-y}} \right. => \left \{ {{54y-y^2-720=0} \atop {x=54-y}} \right. => \left \{ {{D=54^2-4*720=36} \atop {y_1=\frac{-54+6}{-2}=24;\ y_2=\frac{-54-6}{-2}=30}} \right. => \left \{ {{y_1=24;\ y_2=30} \atop {x_1=54-24=30;\ x_2=54-30=24}} \right." align="absmiddle" class="latex-formula">
Ответ: 30 см и 24 см.