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

Question

Millie

1 August, 15:51

+3

Answers (1)

Know the Answer?

Ray Dudley · Answer 1

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