a= vector a

b= vector b

[ ]= numbers in squared brackets are vector components

|a - b| =the magnitude of vectoraminus vectorb

Problem:If

a=[k, 2]andb=[7,6], wherekis a real number, determine all values ofksuch that|a - b| = 5.

The answer in the book says,"10 or 4."

Please help me I have a test tomorrow and I desperately need help on this question.