Question

Find a • b. a = 5i + 7j, b = -4i + 3j

Answer 1

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.

Answer 2

The final answer is C! :)