(A) Equation of Parallel Lines
To find the equation of the straight line which passes through a given point and parallel to another straight line, follow the steps below:
Step 1 : Let the equation of the straight line take the form y = mx + c.
Step 2 : Find the gradient of the straight line from the equation of the straight line parallel to it.
Step 3 : Substitute the value of gradient, m, the x-coordinate and y-coordinate of the given point into y = mx + c to find the value of the y-intercept, c.
Step 4 : Write down the equation of the straight line in the form y = mx + c.
Example 1:
Find the equation of the straight line that passes through the point (–8, 2) and is parallel to the straight line 4y + 3x = 12.
Solution:
(B) Equation of Parallel Lines (Sample Question)
Question 1:
Solution:
Question 1:
The straight lines MN and PQ in the diagram above are parallel. Find the value of q.
Solution:
If two lines are parallel, their gradients are equal.
m1 = m2
mMN = mPQ
60 = 6q + 30
6q = 30
q = 5