[tex]Let\ k:y=m_1x+b_1\ and\ l:y=m_2x+b_2\ then\\\\l\ \perp\ k\iff m_1m_2=-1\to m_2=-\dfrac{1}{m_1}\\----------------------------------\\\text{The slope}\ m_1\ \text{of the line B is equal}\ -\dfrac{3}{4}.\\\text{Let the slope of the line C perpendicular to line B is}\ m_2.\\\text{Then:}\\\\m_2=-\dfrac{1}{-\frac{3}{4}}=\dfrac{4}{3}[/tex]
