since the area of a square is equal to the square of one of its side's length, then the area should be equivalent to [tex] x^{2}[/tex].
[tex] A = x^{2}[/tex] ---> equation (1)
By using pythagoras rule which states that the [tex] x^{2} = hyp^2 - opposite^2[/tex]---> equation (2)
where the opposite side's length is 8 and the hypotenuse side's length is 10
by substituting by the values in equation (2) therefore,
[tex] x^{2} = 10^{2} - 8^{2} [/tex] substitute this value in equation (1) then
[tex] A = x^{2} = 10^{2} -8^{2} [/tex]
where A is the area of the square whose side is x