GCSE Mathematics (9-1)

14.5 Iteration and numerical methods — Practise with help

Work each question first. Open a hint if you need one, then reveal the working to check your method.

Warm-up: remember

  1. Solve 2x+3=112x+3=11.
  2. Expand (x+2)(x+3)(x+2)(x+3).
Answers
  1. x=4x=4. 2. x2+5x+6x^2+5x+6.

Practise with help

1. Use xn+1=12(xn+6/xn)x_{n+1}=\frac12(x_n+6/x_n) from x0=2x_0=2 to find x2x_2.

Hint

Find x1x_1 first. Use that value in the rule again.

Full working

x1=12(2+6/2)=2.5x_1=\frac12(2+6/2)=2.5. Then x2=12(2.5+6/2.5)=2.45x_2=\frac12(2.5+6/2.5)=2.45.

2. Solve y=2x+1y=2x+1 and x+y=10x+y=10.

Hint

Replace yy in the second equation.

Full working

x+2x+1=10x+2x+1=10, so x=3x=3 and y=7y=7.

3. Use xn+1=12(xn+6/xn)x_{n+1}=\frac12(x_n+6/x_n) from x0=2x_0=2 to find x2x_2.

Hint

Find x1x_1 first. Use that value in the rule again.

Full working

x1=2.5x_1=2.5, then x2=2.45x_2=2.45.

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