Is this a right triangle?

Question

Angle A= a. -4/-2 B=-2/2 C=4/-1
Can you please show your work? I don't know how to do this!

Answer 1

If AB² + BC² = AC² then the triangle is right.

AB² = (xB - xA)² + (yB - yA)²
= (- 2 -(-4))² + (2 - (-2))²
= 2² + 4² = 4 + 16 = 20

You calculate BC² and AC² with the same method, and you'll see the triangle is right