Question

If V1 = (2,4) and V2 = (-1,5), then V1*V2is equal to which of the following? A. (-2,20) , B. 18 , C. 22 , D. (8,-5)

Answer 1

B. 18

Explanation

The dot product or scalar product is an algebraic operation that takes two equal-length sequences of numbers (usually coordinate vectors), and returns a single number

it is given by.

$\begin{gathered} u=(u_x,u_y) \\ v=(v_{_x},v_y) \\ u\cdot v=(u_xv_x+u_yv_y) \end{gathered}$

so, we can find the dot product by multiplying the corresponding values in each vector and adding them together

Step 1

get the dot product

let

$\begin{gathered} v_1=(2,4) \\ v_2=(-1,5) \end{gathered}$

then

$\begin{gathered} v_1\cdot v_2=(2\cdot-1)+(4\cdot5) \\ v_1\cdot v_2=-2+20 \\ v_1\cdot v_2=18 \end{gathered}$

therefore, the answer is

B. 18

I hope this helps you