Question

Given the vectors s = 5i-7j and t = 3i-j, find s•t

Answer 1

Recall that:

`\begin{gathered} \text{For all a,b,c,d real numbers:} \\ (ai+bj)\cdot(ci+dj)=ac+bd\text{.} \end{gathered}`

Therefore:

`\begin{gathered} s\cdot t=(5i-7j)\cdot(3i-j), \\ s\cdot t=5\cdot3+(-7)(-1), \\ s\cdot t=15+7, \\ s\cdot t=22. \end{gathered}`

Answer: 22.