User interface language: English | Español

Date November 2008 Marks available 2 Reference code 08N.2.sl.TZ0.1
Level SL only Paper 2 Time zone TZ0
Command term Express Question number 1 Adapted from N/A

Question

Let \(f(x) = 2{x^2} + 4x - 6\) .

Express \(f(x)\) in the form \(f(x) = 2{(x - h)^2} + k\) .

[3]
a.

Write down the equation of the axis of symmetry of the graph of f .

[1]
b.

Express \(f(x)\) in the form \(f(x) = 2(x - p)(x - q)\) .

[2]
c.

Markscheme

evidence of obtaining the vertex     (M1)

e.g. a graph, \(x = - \frac{b}{{2a}}\) , completing the square

\(f(x) = 2{(x + 1)^2} - 8\)     A2     N3

[3 marks]

a.

\(x = - 1\) (equation must be seen)     A1     N1

[1 mark]

b.

\(f(x) = 2(x - 1)(x + 3)\)    A1A1     N2

[2 marks]

c.

Examiners report

Many candidates answered this question with great ease. Still, some found themselves unable to correctly find the vertex algebraically, often mixing the signs of the h and k values. Using the GDC may have been a more fruitful approach. Some candidates did not write the axis of symmetry as an equation.

a.

Many candidates answered this question with great ease. Still, some found themselves unable to correctly find the vertex algebraically, often mixing the signs of the h and k values. Using the GDC may have been a more fruitful approach. Some candidates did not write the axis of symmetry as an equation.

b.

Many candidates answered this question with great ease. Still, some found themselves unable to correctly find the vertex algebraically, often mixing the signs of the h and k values. Using the GDC may have been a more fruitful approach. Some candidates did not write the axis of symmetry as an equation.

c.

Syllabus sections

Topic 2 - Functions and equations » 2.4 » The quadratic function \(x \mapsto a{x^2} + bx + c\) : its graph, \(y\)-intercept \((0, c)\). Axis of symmetry.
Show 48 related questions

View options