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Iterative methodsEdexcel International A Level Maths: Mind map

Recurrence
Rearranging

Iterative methods

$x_{n+1}=f(x_n)$

recurrencelimitsign change
Limit
Change of sign
Exam tips

Exam questions on Iterative methods

  1. The equation x3−4x−3=0x^3-4x-3=0 has a root α\alpha with 2<α<32<\alpha<3. The recurrence relation xn+1=4xn+33x_{n+1}=\sqrt[3]{4x_n+3}, with x0=2x_0=2, is used to find α\alpha.
    Find x2x_2 and x3x_3, giving each to 4 decimal places.2 marks
  2. The equation f(x)=x3+2x−7=0f(x)=x^3+2x-7=0 has a single real root α\alpha.
    Use the iteration xn+1=7−2xn3x_{n+1}=\sqrt[3]{7-2x_n} with x0=1.5x_0=1.5 to find x2x_2, giving your answer to 3 decimal places.2 marks
  3. The function f(x)=ln⁡x+x−3f(x)=\ln x+x-3, for x>0x>0, has a root α\alpha.
    Show that 2<α<2.52<\alpha<2.5.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).