Question

17. Write the equation of a line that is perpendicular to the given line and that passes through the given point.

Answer 1

$\text{Let}\ k:y=m_1x+b_1\ \text{and}\ l:y=m_2x+b_2.\\\\l\ \perp\ k\iff m_1m_2=-1\to m_2=-\dfrac{1}{m_1}\\\\\text{We have the line in point-slope form:}\\\\y-y_1=m(x-x_1)\\\\m-slope\\\\y-2=\dfrac{7}{3}(x+5)\to m_1=\dfrac{7}{3}\\\\\text{therefore}\ m_2=-\dfrac{1}{\frac{7}{3}}=-\dfrac{3}{7}.\\\\\text{We have the slope}\ m=-\dfrac{3}{7}\ \text{and the point}\ (-4,\ 9).\ \text{Substitute:}\\\\y-9=-\dfrac{3}{7}(x-4))\\\\\boxed{y-9=-\dfrac{3}{7}(x+4)}$