Question

Find a • b. a = 5i + 7j, b = -4i + 3j

A. <1, 10>
B. <-20, 21>
C. 1
D. 41

Answer 1

The final answer is C! :)

Answer 2

The dot product of vectors says
`u \cdot v = (x_1)(x_2) + (y_1)(y_2)`, where
`u = x_1i + y_1j` and
`v = x_2i + y_2j`.

Given this, the dot product for these two vectors can be solved:

`(5)(-4) + (7)(3) = -20 + 21 = \boxed{1}`

Our answer is 1, or choice C.