Answer
Area = 64-2$x^2$, $0 \leq x \leq 4$
Work Step by Step
Area of the square = 8*8 = 64
Area of each isosceles triangle = $x^2$/2
Hence area of the resulting figure = area of the square - 4(area of the triangle)
= 64 - 4($x^2$)/2 = 64-2$x^2$
For data to be valid, $2x \leq 8$ ,hence $x \leq 4$
Also x must be non-negative. Hence, $0 \leq x \leq 4$
