Analysis and Approaches for IBDP Maths Ebook 1 | Page 90

Your Practice Set – Analysis and Approaches for IBDP Mathematics
31
Paper 1 Section A – Finding the equations of
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
.
(b) Find the equation of another straight line L
2
such that L
2
is parallel to L
1
and
2
passes through (4, 8) , giving the answer in general form.
[2]
L
[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
(A1) for correct gradient
The equation of L
2
:
y�8 � �2( x� 4)
A1
y�8 � �2x�
8
2x� y�16 � 0
A1 N2
[2]
[3]
Exercise 31
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
.
(b) Find the equation of another straight line L
2
such that L
2
is parallel to L
1
and
2
passes through ( � 2, 5) , giving the answer in general form.
2. The equation of a straight line L
1
is given as 3x� 2y� 4 � 0.
(a) Write down the gradient and the x -intercept of L
1
.
(b) Find the equation of another straight line L
2
such that L
2
is parallel to L
1
and
2
passes through (1, � 7) , giving the answer in general form.
[2]
L
[3]
[2]
L
[3]
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