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Date November 2021 Marks available 2 Reference code 21N.1.SL.TZ0.4
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number 4 Adapted from N/A

Question

Dilara is designing a kite ABCD on a set of coordinate axes in which one unit represents 10cm.

The coordinates of A, B and C are (2, 0), (0, 4) and (4, 6) respectively. Point D lies on the x-axis. AC is perpendicular to BD. This information is shown in the following diagram.

Find the gradient of the line through A and C.

[2]
a.

Write down the gradient of the line through B and D.

[1]
b.

Find the equation of the line through B and D. Give your answer in the form ax+by+d=0, where a, b and d are integers.

[2]
c.

Write down the x-coordinate of point D.

[1]
d.

Markscheme

m=6-04-2=3              (M1)A1

 

[2 marks]

a.

m= -13  -0.333, -0.333333              A1

 

[1 mark]

b.

an equation of line with a correct intercept and either of their gradients from (a) or (b)              (M1)

e.g.  y=-13x+4  OR  y-4=-13x-0


Note: Award (M1) for substituting either of their gradients from parts (a) or (b) and point B or (3, 3) into equation of a line.


x+3y-12=0 or any integer multiple              A1

 

[2 marks]

c.

x= 12            A1

 

[1 mark]

d.

Examiners report

This question was overall well done by most candidates. In part (a) calculating the gradient was correctly done with few errors noted where candidates swapped the y and x coordinates in the gradient formula. Some candidates left their answer as 63 which resulted in a loss of the final mark. There was some confusion with the gradient of a line and the gradient of the perpendicular line in part (a). Some candidates found the perpendicular gradient in part (a). Although many candidates were able to write an appropriate equation of the line through BD, several did not express their answer in the required form ax+by+d=0, where a, b and d are integers. Many final answers were given as y=13x+4 or y-13x-4=0. In part (d), writing the x-coordinate of point D was well done by most candidates. Some candidates wrote a coordinate pair rather than just the x-coordinate as required.

a.

This question was overall well done by most candidates. In part (a) calculating the gradient was correctly done with few errors noted where candidates swapped the y and x coordinates in the gradient formula. Some candidates left their answer as 63 which resulted in a loss of the final mark. There was some confusion with the gradient of a line and the gradient of the perpendicular line in part (a). Some candidates found the perpendicular gradient in part (a). Although many candidates were able to write an appropriate equation of the line through BD, several did not express their answer in the required form ax+by+d=0, where ab and d are integers. Many final answers were given as y=13x+4 or y-13x-4=0. In part (d), writing the x-coordinate of point D was well done by most candidates. Some candidates wrote a coordinate pair rather than just the x-coordinate as required.

b.

This question was overall well done by most candidates. In part (a) calculating the gradient was correctly done with few errors noted where candidates swapped the y and x coordinates in the gradient formula. Some candidates left their answer as 63 which resulted in a loss of the final mark. There was some confusion with the gradient of a line and the gradient of the perpendicular line in part (a). Some candidates found the perpendicular gradient in part (a). Although many candidates were able to write an appropriate equation of the line through BD, several did not express their answer in the required form ax+by+d=0, where ab and d are integers. Many final answers were given as y=13x+4 or y-13x-4=0. In part (d), writing the x-coordinate of point D was well done by most candidates. Some candidates wrote a coordinate pair rather than just the x-coordinate as required.

c.

This question was overall well done by most candidates. In part (a) calculating the gradient was correctly done with few errors noted where candidates swapped the y and x coordinates in the gradient formula. Some candidates left their answer as 63 which resulted in a loss of the final mark. There was some confusion with the gradient of a line and the gradient of the perpendicular line in part (a). Some candidates found the perpendicular gradient in part (a). Although many candidates were able to write an appropriate equation of the line through BD, several did not express their answer in the required form ax+by+d=0, where ab and d are integers. Many final answers were given as y=13x+4 or y-13x-4=0. In part (d), writing the x-coordinate of point D was well done by most candidates. Some candidates wrote a coordinate pair rather than just the x-coordinate as required.

d.

Syllabus sections

Topic 2—Functions » SL 2.1—Equations of straight lines, parallel and perpendicular
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Topic 2—Functions

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