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g(x) = e^(x) + x - 6 (a) Show that the equation g(x) = 0 can be written as x = ln(6 - x) + 1, x < 6 (2) The root of g(x) = 0 is α - Edexcel - A-Level Maths Pure - Question 23 - 2013 - Paper 1

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g(x)-=-e^(x)-+-x---6--(a)-Show-that-the-equation-g(x)-=-0-can-be-written-as--x-=-ln(6---x)-+-1,--x-<-6--(2)--The-root-of-g(x)-=-0-is-α-Edexcel-A-Level Maths Pure-Question 23-2013-Paper 1.png

g(x) = e^(x) + x - 6 (a) Show that the equation g(x) = 0 can be written as x = ln(6 - x) + 1, x < 6 (2) The root of g(x) = 0 is α. The iterative formula x_{n+... show full transcript

Worked Solution & Example Answer:g(x) = e^(x) + x - 6 (a) Show that the equation g(x) = 0 can be written as x = ln(6 - x) + 1, x < 6 (2) The root of g(x) = 0 is α - Edexcel - A-Level Maths Pure - Question 23 - 2013 - Paper 1

Step 1

Show that the equation g(x) = 0 can be written as x = ln(6 - x) + 1, x < 6

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Answer

To show that g(x) = e^(x) + x - 6 can be rewritten, we set g(x) = 0. This gives:

ex+x6=0e^{x} + x - 6 = 0

Rearranging this equation leads us to:

ex=6xe^{x} = 6 - x

Taking the natural logarithm of both sides gives:

x=ln(6x)x = ln(6 - x)

Now, adding 1 to both sides yields:

x=ln(6x)+1x = ln(6 - x) + 1

As long as x remains less than 6, this manipulation holds true.

Step 2

Calculate the values of x_1, x_2, and x_3 to 4 decimal places.

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Answer

Using the iterative formula provided: xn+1=ln(6xn)+1x_{n+1} = ln(6 - x_n) + 1

Calculation of x_1:

Starting with x_0 = 2:

x1=ln(62)+1=ln(4)+12.3863x_{1} = ln(6 - 2) + 1 = ln(4) + 1 ≈ 2.3863

Calculation of x_2:

Using x_1 to find x_2:

x2=ln(62.3863)+1=ln(3.6137)+12.2847x_{2} = ln(6 - 2.3863) + 1 = ln(3.6137) + 1 ≈ 2.2847

Calculation of x_3:

Using x_2 to find x_3:

x3=ln(62.2847)+1=ln(3.7153)+12.3125x_{3} = ln(6 - 2.2847) + 1 = ln(3.7153) + 1 ≈ 2.3125

Thus the values are:

  • x_1 ≈ 2.3863
  • x_2 ≈ 2.2847
  • x_3 ≈ 2.3125

Step 3

By choosing a suitable interval, show that α = 2.307 correct to 3 decimal places.

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Answer

To find α correctly to three decimal places, we start by finding an interval that contains the root α.

Choosing the interval:

Based on previous calculations:

  • g(2.3065) = e^(2.3065) + 2.3065 - 6 ≈ -0.0002
  • g(2.3075) = e^(2.3075) + 2.3075 - 6 ≈ 0.0044

Since g(2.3065) is slightly less than 0 and g(2.3075) is slightly more than 0, it shows that the root lies in the interval [2.3065, 2.3075].

Finalizing the estimate for α:

Using bisection or any iterative method on this interval would bring us to a value α = 2.307 (when rounded to three decimal places). Thus, we have shown that α = 2.307.

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