It is given that the slope is -2.
[tex]m_1=-2[/tex]Recall that
[tex]\begin{gathered} \text{If }m_1\text{ and }m_2\text{ are perpendicular then it can be written as } \\ m_2=-\frac{1}{m_1} \end{gathered}[/tex][tex]\text{Substitute }m_1=-2,\text{ we get}[/tex][tex]m_2=-\frac{1}{-2}=\frac{1}{2}[/tex]Hence the slope 1/2 that is perpendicular to -2.