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If z=4+i, what is 1/z? (in the form a+bi)

1/z =1/(4+i) Multiply both top and bottom by the complex conjugate, z* = 4 - i, 1/z = (4-i)/((4+i)(4-i)) = (4-i)/(16+4i-4i-i²) = (4-i)/17 ans: 4/17 - i/17

Answered by Rachel H. • Further Mathematics tutor

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Prove by induction that (n^3)-n is divisible by 3 for all integers n>0 (typical fp1 problem)

Let P(n) be the statement “(n^3)-n is divisible by 3”

First we’ll examine the base case: P(1)

(n^3)-n=1^3-1=1-1=0

0=3*0, so is divisible by 3, and so P(1) is true

Now assume fo...

Answered by Tom N. • Further Mathematics tutor

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How do I sketch accurate graphs for rational functions in a short amount of time? (I.e. A step by step guide of sketching graphs)

Often in Further Pure modules for various exam boards a common question in the exam paper will be to sketch a graph for a rational function. The step by step aproach I used is as follows:

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Answered by Darshan H. • Further Mathematics tutor
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solve the equation 4cos^2(x) -15sin(x) = 13

We first want to get every term in terms of the same variable, namely sin(x). to do so, we will use the identity sin^2(x) +cos^2(x) = 1 to get: 4(1-sin^2(x)) -15sin(x) -13 = 0. which we can then rewrite a...

Answered by Max G. • Further Mathematics tutor

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The function f is defined for x > 0 by f (x) = x^1n x. Obtain an expression for f ′ (x).

By taking the natural log on both sides we can see that: ln(f(x)) = ln(x)^2 This is a more familiar expression that we know how to differentiate LHS: f '(x)/f(x), RHS: 2*ln(x)/x By re...

Answered by Steven E. • Further Mathematics tutor

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