x+y=28/2 x+y=14
x=14-y
x³+x²y-xy²-y³=0
x²(x+y)-y²(x+y)=0
(x+y)(x²-y²)=0
(x+y)²(x-y)=0
x=y
x+y=14
x=y=7
S=7*7=49