a = vector a
b = vector b
[ ] = numbers in squared brackets are vector components
|a - b| = the magnitude of vector a minus vector b
If a=[k, 2] and b=[7,6], where k is a real number, determine all values of k such 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.