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Perplex

Paper 3 Practice

Paper 3 Practice

[Maximum mark: 23]

This questions asks you to investigate the recursive nature of the derivatives of ​1−x1​​ and how this impacts the Maclaurin series expansion.


Consider the function ​f(x)=1−x1​, ​x=1.

  1. Find the value of ​f(0.5).

    [1]

    To earn a crown, get your answer ready before you reveal the options!

  2. Show that ​(1−x)f′(x)−f(x)=0.

    [2]
  3. By differentiating the equation in (b), show that ​(1−x)f′′(x)−2f′(x)=0.

    [3]

Let ​f(n)​ be the ​nth​ derivative of ​f.

  1. Using mathematical induction, prove that ​(1−x)f(n)(x)−nf(n−1)(x)=0​ for all ​n∈N.

    [6]
  2. Hence solve the differential equation ​dxdy​=1−x3y​.

    [3]
  3. Using (d), show that ​f(n)(0)=n!​ for all ​n∈N.

    [2]
  4. Hence find the Maclaurin series expansion for ​f(x).

    [3]
  5. Use the Maclaurin series expansion to find the value of ​f(21​), and comment on the result.

    [3]

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[Maximum mark: 23]

This questions asks you to investigate the recursive nature of the derivatives of ​1−x1​​ and how this impacts the Maclaurin series expansion.


Consider the function ​f(x)=1−x1​, ​x=1.

  1. Find the value of ​f(0.5).

    [1]

    To earn a crown, get your answer ready before you reveal the options!

  2. Show that ​(1−x)f′(x)−f(x)=0.

    [2]
  3. By differentiating the equation in (b), show that ​(1−x)f′′(x)−2f′(x)=0.

    [3]

Let ​f(n)​ be the ​nth​ derivative of ​f.

  1. Using mathematical induction, prove that ​(1−x)f(n)(x)−nf(n−1)(x)=0​ for all ​n∈N.

    [6]
  2. Hence solve the differential equation ​dxdy​=1−x3y​.

    [3]
  3. Using (d), show that ​f(n)(0)=n!​ for all ​n∈N.

    [2]
  4. Hence find the Maclaurin series expansion for ​f(x).

    [3]
  5. Use the Maclaurin series expansion to find the value of ​f(21​), and comment on the result.

    [3]

Ask Plex AI about this problem

Get hints, ask questions, and work through this problem step by step

I'm Plex, here to help with problems on this worksheet!