If a question asks about perpendicular lines, the slope of the perpendicular line is ALWAYS THE OPPOSITE RECIPROCAL OF THE GIVEN LINE
For instance, if we have a line with a slope of 3, the slope of the line that is perpendicular is -1/3.
You get this by flipping the numerator and denominator of the original slope and multiplying by -1.
So for the line y=-.25x+3, the perpendicular slope is 4.
1. flip the fraction---> -.25----> -4
2. multiply by -1 -----> -4*-1 = 4
