Is it a right triangle? Explain.

Yep....by the Pythagorean Theorem.......if the sum of the squares of the two shorter sides = the square on the longer side, it's a right triangle....so.....

3^2   + 4^2   = 5^2

9  +  16   = 25

I happen to KNOW that it is, but you can prove it with the Pythagorean Theory

a^2 + b^2 = c^2

Does   3^2 + 4^2 = 5^2

            9    + 16  = 25       Yep, it's a Right Triangle !