The slope of the line is , so we want the tangent line with a slope of , since that line is perpendicular to this one (if two lines are perpenicular, then their slopes are the negative inverses of each other).
Let's find the formula for the slope of the tangent line at any point of the curve. This is given by the derivative.
This is the formula for the slope, we want the slope to be -2, so let's solve for that.
So the tangent line with a slope of -2 occurs at the point (2,-5) on the curve. Now we have everything to find the equation of the tangent line.
Using (x,y) = (2,-5) and m = -2, we have by the point-slope form: