 
Summary: Math 2210 Problem Set 2
Key
Show your work!
Problem 1 Suppose that the bookstore sells 2" notebooks for $7.50, packs of 200 sheets of filler paper for
$4.00, and cartridge erasers for $1.50. If the bookstore sells x 2" notebooks, y packs of 200 sheets of filler
paper, and z cartridge erasers then what does (7.5, 4, 1.5) · (x, y, z) measure?
Solution 1 Total income from the sales of 2" notebooks, filler paper, and cartridge erasers.
Problem 2 Solve exactly:
(1, 1, 1) · (1, x, x2
) = 0
Solution 2 If x2 + x + 1 = 0 then
x =
1 ±
1  4
2
=
1 ±
3i
