Find the dot product, a • b. a = 6i + 5j, b = - 5i + 4j

We are to find the dot product of the given vectors. To find this just multiply the coefficients of i terms (horizontal components) and multiply the coefficients of j terms (vertical components), and add the two products together, as shown below:

a. b = (6i + 5j). (-5i+4j)

a. b = 6 (-5) + 5 (4)

a. b = - 30 + 20

a. b = - 10

The dot product results in a scalar quantity, so you only get a magnitude not a vector.