- #1

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## Homework Statement

Which of the following functions is

*not*an inner product in [tex]\mathbb{R}^2[/tex], where u=(a, b), v=(c,d)?

a. <u,v> = ac+bd

b. <u,v> = 4ad+7bc

c. <u,v> = ac/2+bd/3

d. <u,v> = 2ac+9bd

## Homework Equations

None

## The Attempt at a Solution

u x v = det(u v) = ad-bc

I don't see how ANY of these answers could be right. Any ideas?