Apps. and Interpretation for IBDP Maths Ebook 1 | Page 105

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Paper 1 – Finding the Equation of a Straight Line
Example
A straight line L passes through the points A(3, 2) and B(10,16) .
(a) Find the equation of L , giving the answer in general form.
(b) Write down the x -intercept and the y -intercept of L .
(c) Write down the coordinates of the midpoint of AB .
[3]
[2]
[1]
Solution
(a)
The gradient of L
16 � 2
�
(A1) for correct formula
10 � 3
� 2
The equation of L :
y� 2 � 2( x� 3)
(M1) for substitution
y� 2 � 2x�
6
2x� y� 4 � 0
A1 N3
(b) The x -intercept of L is 2 A1
The y -intercept of L is � 4
A1 N2
(c) (6.5, 9) A1 N1
[3]
[2]
[1]
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