PLS HELP 1ST ANSWER GETS BRAINLIEST!!!!!Which math sentence can be used to determine if this triangle is a right triangle?

A triangle has side lengths 21, 20, and hypotenuse 29.
20 + 21 = 29
20 squared + 21 squared = 29 squared
29 + 21 = 20
29 squared + 21 squared = 20 squared