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put this solution on YOUR website!If the rectangle is a square, than all of the sides (x) are equal. Since the triangles formed are right triangles and the hypotenuse is the diagonal, use the Pythagorean Theorem to solve:
a^2+b^2=c^2
.
a=one side=x
b=another side=x
c=the hypotenuse=3
.
Plug-in the values and solve for the x-term
x^2+x^2=3^2
2x^2=9
2x^2/2=9/2
x^2=9/2

=

x=

x=

[rationalize the denominator]
x=
.
check by plugging all of the values back into:
a^2+b^2=c^2

+

=3^2