Chapter 12 - Exponential Functions and Logarithmic Functions - 12.7 Applications of Exponential Functions and Logarithmic Functions - 12.7 Exercise Set - Page 837: 50

$y=-2x+8$

$y=\frac{1}{2}x+3$ The slope of any line that is perpendicular to the line given by $y=\frac{1}{2}x+3$ has a slope which is the opposite of the reciprocal of $\frac{1}{2}$, or $-2$. Substitute $-2$ for $m$ and $8$ for $b$ in the slope-intercept equation: $y=-2x+8$