Step 1: Find the slope of the perpendicular line

NOTE: i) Parallel lines have the same slope.

ii) Perpendicular lines have slopes that are opposite reciprocals, like

\frac{a}{b} \text{ and } \frac{-b}{a}. The slopes also have a product of -1

Step 2: Use the slope of line and a point on line to find its y-intercept.

EXAMPLE: Plug the slope m = -2 and the point (-6, 4) into the slope- intercept formula. Then solve for the y-intercept b.

y = mx + b

4 = -2(-6) + b

Step 3: Use the slope of line and the y-intercept of line to find the equation of the line.

EXAMPLE: Plug the slope m = -2 and the y-intercept b = -8 into the slope- intercept formula.

y = mx + b

y = -2x + -8

Step 4: Solve the equation for required coordinate

NOTE: Apply the factorization method to solve the equation or

**Quadratic formula** = \frac{-b\pm\sqrt{b^2\ -\ 4ac}}{4a}