Answer:
Third answer (she is incorrect because she should have squared each leg length and then found the sum.)
Step-by-step explanation:
The pythagorean theorem states that a²+b²=c². This is not equivalent to (a+b)²=c² (due to FOIL expansion, this expands to a²+2ab+b²=c²).
This matches with the third answer, as she has to do a² and b≥ separately.
**This question involves expanding perfect squares, which you may wish to revise. I'm always happy to help!