Answer
$46$
Work Step by Step
Use
$\vec{a}\cdot\vec{b}=a_{x}b_{x}+a_{y}b_{y}+a_{z}b_{z}\qquad$ (3-23)
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$\vec{a}=3.0\hat{i}+5.0\hat{j}+0\hat{k}$
$\vec{b}=2.0\hat{i}+4.0\hat{j}+0\hat{k}$
$(\vec{a}+\vec{b})=(3.0+2.0)\hat{i}+ (5.0+4.0)\hat{j}$
$=5.0\hat{i}+9.0\hat{j}$
$(\vec{a}+\vec{b})\cdot\vec{b } = (5.0)(2.0)+(9.0)(4.0)=46$
