17N.1.AHL.TZ0.H_1

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

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

${\log }_2(x^2-9)=4$     (M1)

$x^2-9=2^4(=16)$     M1A1

$x^2=25$

$x=\pm 5$     (A1)

$x=5$     A1

[5 marks]

[N/A]