Right triangles must follow the pythagorean theorem, so a^2+b^2=c^2.
Let's find a^2 and b^2 by squaring the first 2 side lengths.
(x^2-1)^2= x^4-2x^2+1
(2x)^2= 4x^2
Then add the two to find c^2
x^4+ 2x^2 +1= c^2
Root both sides
x^2+1=c
Since the side lengths can be plugged into the pythagorean theorem, the side lengths must represent a right triangle.
Hope this helps!
