Apps. and Interpretation for IBDP Maths Ebook 1 | Page 107

30
Paper 1 – Parallel and Perpendicular Lines
Example
The equation of a straight line L
1
is given as 2x� y�10 � 0 .
(a) Write down the gradient and the x -intercept of L
1
.
[2]
(b) Find the equation of another straight line L
2
such that L
2
is parallel to L
1
and L
2
passes through (4, 8) , giving the answer in general form.
[3]
Solution
(a) The gradient of L
1
is � 2
A1
The x -intercept of L
1
is 5 A1 N2
(b) The gradient of L
2
is � 2
The equation of L
2
:
(A1) for correct gradient
[2]
y�8 � �2( x� 4)
(M1) for substitution
y�8 � �2x�
8
2x� y�16 � 0
A1 N3
[3]
10
Exercise 30
1. The equation of a straight line L
1
is given as x� 2y�16 � 0 .
(a) Write down the gradient and the y -intercept of L
1
.
[2]
(b) Find the equation of another straight line L
2
such that L
2
is parallel to L
1
and L
2
passes through ( � 2, 5) , giving the answer in general form.
[3]
97
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