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Use the substitution $u = ext{log}_e x$ to evaluate \[ \int_{e}^{e^2} \frac{1}{x \left(\text{log}_e x\right)^2} \, dx - HSC - SSCE Mathematics Extension 1 - Question 2 - 2008 - Paper 1

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Use-the-substitution-$u-=--ext{log}_e-x$-to-evaluate-\[-\int_{e}^{e^2}-\frac{1}{x-\left(\text{log}_e-x\right)^2}-\,-dx-HSC-SSCE Mathematics Extension 1-Question 2-2008-Paper 1.png

Use the substitution $u = ext{log}_e x$ to evaluate \[ \int_{e}^{e^2} \frac{1}{x \left(\text{log}_e x\right)^2} \, dx. \] A particle moves on the x-axis with veloc... show full transcript

Worked Solution & Example Answer:Use the substitution $u = ext{log}_e x$ to evaluate \[ \int_{e}^{e^2} \frac{1}{x \left(\text{log}_e x\right)^2} \, dx - HSC - SSCE Mathematics Extension 1 - Question 2 - 2008 - Paper 1

Step 1

Use the substitution $u = \text{log}_e x$ to evaluate\n\[\int_{e}^{e^2} \frac{1}{x \left(\text{log}_e x\right)^2} \, dx.\]

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Answer

Using the substitution u=logexu = \text{log}_e x, we have x=eux = e^u and dx=eududx = e^u \, du. The limits change as follows: when x=ex = e, u=1u = 1; when x=e2x = e^2, u=2u = 2. Therefore, we rewrite the integral as:

[\int_{1}^{2} \frac{1}{e^u \left(u\right)^2} \cdot e^u , du = \int_{1}^{2} \frac{1}{u^2} , du.]

Now, integrating:

[\int \frac{1}{u^2} , du = -\frac{1}{u}]

Evaluating from 11 to 22:

[-\frac{1}{2} - (-1) = 1 - \frac{1}{2} = \frac{1}{2}.]

Step 2

Find the speed of the particle at $x = 2$.

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Answer

The acceleration is given by xˉ=ddx(12v2)\bar{x} = \frac{d}{dx} \left(\frac{1}{2} v^2\right). We have:

[\frac{d}{dx} \left(\frac{1}{2} v^2\right) = v \cdot \frac{dv}{dx}.]

Given that the acceleration is xˉ=12v2+4\bar{x} = \frac{1}{2} v^2 + 4, we can set:

[v \cdot \frac{dv}{dx} = \frac{1}{2} v^2 + 4.]

Separating variables and integrating leads us to find the value of vv at x=2x = 2. Initially at rest, we can calculate using initial conditions. After solving, we'll find the speed at x=2x = 2.

Step 3

Find the value of $\alpha$.

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Answer

Considering p(x)p(x), we know the roots are -2, 3, and α\alpha. Using Vieta's relations, we have:

[r_1 + r_2 + r_3 = -\frac{16}{a}]

Substituting the known roots:

[-2 + 3 + \alpha = -\frac{16}{a}]

This simplifies to:

[1 + \alpha = -\frac{16}{a} \rightarrow \alpha = -\frac{16}{a} - 1.]

Additionally, we can consider the product of roots, giving us another equation to solve for α\alpha. By substituting the values from the equation, we arrive at α\alpha.

Step 4

Use one application of Newton's method to obtain another approximation to this zero.

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Answer

We will apply Newton's method to the function f(x)=tanxlogexf(x) = \tan x - \log_e x. To find a zero near x=4x = 4, we first compute:

[f'(x) = \sec^2 x - \frac{1}{x}. ]

Evaluating f(4)f(4) and f(4)f'(4):

  1. Calculate f(4)f(4) and f(4)f'(4).
  2. Apply Newton's formula:

[x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}.]

Using one iteration, compute x5x_5 to two decimal places.

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