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Date	November 2017	Marks available	5	Reference code	17N.1.AHL.TZ0.H_1
Level	Additional Higher Level	Paper	Paper 1	Time zone	Time zone 0
Command term	Solve	Question number	H_1	Adapted from	N/A

Question

Solve the equation ${log}_{2} (x + 3) + {log}_{2} (x - 3) = 4$ ${\log _2}(x + 3) + {\log _2}(x - 3) = 4$ .

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

${log}_{2} (x + 3) + {log}_{2} (x - 3) = 4$ ${\log _2}(x + 3) + {\log _2}(x - 3) = 4$

${log}_{2} (x^{2} - 9) = 4$ ${\log _2}({x^2} - 9) = 4$ (M1)

$x^{2} - 9 = 2^{4} (= 16)$ ${x^2} - 9 = {2^4}{\text{ }}( = 16)$ M1A1

$x^{2} = 25$ ${x^2} = 25$

$x = \pm 5$ $x = \pm 5$ (A1)

$x = 5$ $x = 5$ A1

[5 marks]

Examiners report

[N/A]

Syllabus sections

Topic 1—Number and algebra » SL 1.5—Intro to logs

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