# Form 2 Mathematics equations of straight lines online lessons

In this lesson, we are going to learn about Equation of straight lines: Perpendicular Lines

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**Answer Text:**

Perpendicular Lines

-If two straight lines are perpendicular each other, then the product of their gradients will be equal to -1.

-In other words if L1 with a gradient g1 and L2 with g2 are perpendicular lines then.

g1 x g2 =-1.

g1 = #-1/g_2#

Example 1. A line L1 passes though point (1, 2) and has a gradient of 5. Another line L2, is perpendicular to L1 and meets it at a point where x = 4. Find the equation for L2 in the form of y = mx + c

Example 2

P (5, -4) and Q (-1, 2) are points on a straight line. Find the equation of the perpendicular bisector of PQ: giving the answer in the form y = mx + c