we know that
the area of the complete square is equal to
[tex] As=b^{2} [/tex]
where
b is the length side of the square
[tex] b=8m [/tex]
so
[tex] As=8^{2} [/tex]
[tex] As=64[/tex]m²
the area of one corner is equal to the area of a triangle
[tex] \frac{x^{2}}{2} [/tex]
so
the area of [tex] 4 [/tex] corners is equal to
[tex] \frac{x^{2}}{2}*4=2x^{2} [/tex]
the area A of the resulting figure as a function of x is equal to
area of the square minus the area of [tex] 4 [/tex] corners
[tex] A=(64-2x^{2}) [/tex]m²
the answer is
[tex] A=(64-2x^{2}) [/tex]m²