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Date May 2011 Marks available 2 Reference code 11M.1.sl.TZ2.5
Level SL only Paper 1 Time zone TZ2
Command term Find Question number 5 Adapted from N/A

Question

The straight line \(L\) passes through the points \({\text{A}}( - 1{\text{, 4}})\) and \({\text{B}}(5{\text{, }}8)\) .

Calculate the gradient of \(L\) .

[2]
a.

Find the equation of \(L\) .

[2]
b.

The line \(L\) also passes through the point \({\text{P}}(8{\text{, }}y)\) . Find the value of \(y\) .

[2]
c.

Markscheme

\(\frac{{8 - 4}}{{5 - ( - 1)}}\)     (M1)

Note: Award (M1) for correct substitution into the gradient formula.

 

\(\frac{2}{3}{\text{ }}\left( {\frac{4}{6}{\text{, }}0.667} \right)\)     (A1)     (C2)

[2 marks]

a.

\(y = \frac{2}{3}x + c\)     (A1)(ft)

Note: Award (A1)(ft) for their gradient substituted in their equation.


\(y = \frac{2}{3}x + \frac{{14}}{3}\)     (A1)(ft)     (C2)

Notes: Award (A1)(ft) for their correct equation. Accept any equivalent form. Accept decimal equivalents for coefficients to 3 sf.

 

OR

\(y - {y_1} = \frac{2}{3}(x - {x_1})\)     (A1)(ft)

Note: Award (A1)(ft) for their gradient substituted in the equation.

 

\(y - 4 = \frac{2}{3}(x + 1)\)     OR     \(y - 8 = \frac{2}{3}(x - 5)\)     (A1)(ft)     (C2)

Note: Award (A1)(ft) for correct equation.

[2 marks]

b.

\(y = \frac{2}{3} \times 8 + \frac{{14}}{3}\)     OR     \(y - 4 = \frac{2}{3}(8 + 1)\)     OR     \(y - 8 = \frac{2}{3}(8 - 5)\)     (M1)

Note: Award (M1) for substitution of \(x = 8\) into their equation.

 

\(y = 10\) (\(10.0\))     (A1)(ft)     (C2)

Note: Follow through from their answer to part (b).

[2 marks]

c.

Examiners report

Generally, a well answered question with many candidates achieving full marks. Indeed, marks which tended to be lost were as a result of premature rounding rather than method. On a number of scripts, part (a) produced a rather curious wrong answer of \(8.2\) following a correct gradient expression. It would seem that this was as a result of typing into the calculator \(8 - 4 ÷ 5 + 1\).

a.

Generally, a well answered question with many candidates achieving full marks. Indeed, marks which tended to be lost were as a result of premature rounding rather than method.

b.

Generally, a well answered question with many candidates achieving full marks. Indeed, marks which tended to be lost were as a result of premature rounding rather than method.

c.

Syllabus sections

Topic 5 - Geometry and trigonometry » 5.1 » Equation of a line in two dimensions: the forms \(y = mx + c\) and \(ax + by + d = 0\) .
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