## Point-slope

Consider one straight line passing through the points (-5, 1) and (2,0), while another straight line passes through points (-1, -9) and (0, -3). Are these lines parallel, perpendicular, or do they intersect at a non 90° angle?

Hint
Given two points, the slope is:
$$m=\frac{rise}{run}=\frac{y_2-y_1}{x_2-x_1}$$$Hint 2 Slopes of perpendicular lines are the negative reciprocals of each other. Parallel lines have identical slopes. The first step is to find the slope values for both lines. Given two points, the slope is: $$m=\frac{rise}{run}=\frac{y_2-y_1}{x_2-x_1}$$$
$$m_1=\frac{0-1}{2-(-5)}=-\frac{1}{7}$$$$$m_2=\frac{-3-(-9)}{0-(-1)}=\frac{6}{1}=6$$$
Because $$m_1$$ and $$m_2$$ differing slopes and not negative reciprocals of each other, these two slopes intersect at a non 90° angle. Parallel lines have identical slopes, while perpendicular lines have negative reciprocal slopes.
non 90° angle