Question 98260
x= length of side
x+3=lendth of diagonal
we have a right angle isoscoles triangle.
a^2+b^2=c^2
so 2x^2=(x+3)^2
2x^2=x^2+6x+9
subtract 2x^2 from each side: -x^2+6x+9=0
multiply -1 times both sides: x^2-6x-9=0
Quadratic formula: x=7.24... and x=-1.24...(extraneous)
the diagonal=10.24...
Check:
2(7.24...)^2=(10.24...)^2
104.8=104.9 (.1 rounding error)
Ed