# 9.3.7 Straight Lines, PT3 Focus Practice

Question 13:
Diagram shows a straight line ST and a straight line PQ drawn on a Cartesian plane.  ST is  parallel to PQ. Given that equation of the straight line ST is 2y = 8x + 3.

Find,
(a)  the equation of the straight line PQ,
(b)  the x-intercept of the straight line PQ.
[ 5 marks ]
Solution:
(a)
$\begin{array}{l}2y=8x+3\\ y=4x+\frac{3}{2}\end{array}$
m = 4
4 = 4 (6) + c
c = 2
Using formula, y = mx + c
equation of the straight line PQ is y = 4x 20.

(b)
y = 4x 20, at x-intercept, y = 0
4x – 20 = 0,   y= 0
x = 5   or   x-intercept = 5