# How would I find a line perpendicular to: y=2x+5?

Perpendicular lines have gradients whose product is $- 1$.
Straight lines in standard form $y = m x + c$ has gradient m and y-intercept c.
So $y = 2 x + 5$ has gradient $2$.
So any line of gradient $- \frac{1}{2}$ will be perpendicular to this line,
ie. any line of form $y = - \frac{1}{2} x + c$