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Date November 2012 Marks available 2 Reference code 12N.1.sl.TZ0.8
Level SL only Paper 1 Time zone TZ0
Command term Write down Question number 8 Adapted from N/A

Question

The straight line, L1, has equation y = −2x + 5.

Write down the gradient of L1 .

[1]
a.

Line L2, is perpendicular to line L1, and passes through the point (4, 5) .

(i) Write down the gradient of L2 .

(ii) Find the equation of L2 .

[3]
b.

Line L2, is perpendicular to line L1, and passes through the point (4, 5) .

Write down the coordinates of the point of intersection of L1 and L2 .

[2]
c.

Markscheme

–2     (A1)     (C1)

Note: Do not accept \(\frac{{ - 2}}{1}\)

[1 mark]

a.

(i) \(\frac{1}{2}(0.5)\)     (A1)(ft)

Note: Follow through from their part (a).

 

(ii) \(5 = \frac{1}{2}(4) + c\)     (M1)

Note: Award (M1) for their gradient substituted correctly.

 

\(y = \frac{1}{2}x + 3\)     (A1)(ft)

Note: Follow through from their part (b)(i).

 

OR

\(y - 5 = \frac{1}{2}(x - 4)\)     (M1)(A1)(ft)     (C3)

Notes: Award (M1) for their gradient substituted correctly, (A1)(ft) for 5 and 4 seen in the correct places. Follow through from their part (b)(i).

 

[3 marks]

b.

(0.8, 3.4) or \(\left( {\frac{4}{5},\frac{{17}}{5}} \right)\)     (A1)(ft)(A1)(ft)     (C2)

Notes: Accept x = 0.8 and y = 3.4. Award (A1)(ft) for an attempt to solve the equations analytically, (attempt to eliminate either x or y), or graphically with a sketch (two reasonably accurate straight line graphs (from their answer to part (b)) and an indication of scale). Follow through from their L2 if it intersects L1, OR follow through from their equation, or expression in x, from their part (b)(ii). Award at most (A1)(ft)(A0)(ft) if brackets missing. Award (A0)(ft)(A1)(ft) for an answer of (0, 5) following an equation (or expression in x) of the form y = mx + 5 (m ≠ –2) found in part (b).

[2 marks]

c.

Examiners report

The majority of candidates were able to write down the gradient of the straight line in part (a) but a correct answer for the gradient of the perpendicular proved to be more elusive in part (b)(i). Many however recovered in the remainder of the question as they were able to find the equation of a line using their gradient and the coordinates of a point on the line but, in some case, did not always show clear working. A significant minority of candidates, who attempted to substitute (4, 5) into the equation y = mx + c , incorrectly identified the value of c as 5.

a.

The majority of candidates were able to write down the gradient of the straight line in part (a) but a correct answer for the gradient of the perpendicular proved to be more elusive in part (b)(i). Many however recovered in the remainder of the question as they were able to find the equation of a line using their gradient and the coordinates of a point on the line but, in some case, did not always show clear working. A significant minority of candidates, who attempted to substitute (4, 5) into the equation y = mx + c , incorrectly identified the value of c as 5.

b.

The majority of candidates were able to write down the gradient of the straight line in part (a) but a correct answer for the gradient of the perpendicular proved to be more elusive in part (b)(i). Many however recovered in the remainder of the question as they were able to find the equation of a line using their gradient and the coordinates of a point on the line but, in some case, did not always show clear working. A significant minority of candidates, who attempted to substitute (4, 5) into the equation y = mx + c , incorrectly identified the value of c as 5.

c.

Syllabus sections

Topic 5 - Geometry and trigonometry » 5.1 » Points of intersection of lines.

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