Cambridge International Mathematics

Example 26 Self Tutor

Solve 2 x^2 ¡ 3 x¡4=0 using technology, giving your answers correct

to 3 decimal places.

Consider y=2x^2 ¡ 3 x¡ 4 :

The following graphics calculator screen dumps show successive steps:

So, x¼¡ 0 : 851 or 2 : 351.

EXERCISE 21I

1

2

The problems in this section can all be converted to algebraic form asquadratic equations. They can all

be solved usingfactorisation, thequadratic formulaortechnology.

However, if an equation can be solved by factorisation, it is expected that you will use this method.

PROBLEM SOLVING METHOD

Step 1: Carefully read the question until you understand the problem.

A rough sketch may be useful.

Step 2: Decide on the unknown quantity and label itx, say.

Step 3: Use the information given to find an equation which containsx.

Step 4: Solve the equation.

Step 5: Check that any solutions satisfy the equation and are realistic to the problem.

Step 6: Write your answer to the question in sentence form.

J PROBLEM SOLVING [2.10, 3.2]

Obviously you

cannot provide

screen dumps in

your answer. You

should sketch the

graph instead.

Use technology to solve, correct to 3 decimal places:

a x^2 +4x+2=0 b x^2 +6x¡2=0 c 2 x^2 ¡ 3 x¡7=0

d 3 x^2 ¡ 7 x¡11 = 0 e 4 x^2 ¡ 11 x¡13 = 0 f 5 x^2 +6x¡17 = 0

Use technology to solve, correct to 3 decimal places:

a^12 x^2 ¡^13 x¡^14 =0 b x^2 +

p

2 x¡3=0 c

p

3 x^2 ¡ 3 x+1=0

Quadratic equations and functions (Chapter 21) 447

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Y:\HAESE\IGCSE01\IG01_21\447IGCSE01_21.CDR Monday, 27 October 2008 2:10:08 PM PETER