Question

A student is asked to calculate the value of 752 − 702 using the identity x2 − y2 = (x − y)(x + y). The student's steps are shown below.

Step 1: 752 − 702 = (75 − 70)(75 + 70)

Step 2: = (5)(155)

Step 3: = (5)(150) + 5(5)

Step 4: = 750 + 25

Step 5: = 775

The correct answer should be 725. In which step did the student make his first error?
Step 1
Step 2
Step 3

Answer 1

Step 2, 5*155= 775,which means the steps after that would make the answer even more variable