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Consider the three vectors $ar{a} = ar{O A}, ar{b} = ar{O B}$ and $ar{c} = ar{O C}$, where O is the origin and the points A, B and C are all different from each other and the origin - HSC - SSCE Mathematics Extension 2 - Question 15 - 2024 - Paper 1

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Question 15

Consider-the-three-vectors-$ar{a}-=-ar{O-A},-ar{b}-=-ar{O-B}$-and-$ar{c}-=-ar{O-C}$,-where-O-is-the-origin-and-the-points-A,-B-and-C-are-all-different-from-each-other-and-the-origin-HSC-SSCE Mathematics Extension 2-Question 15-2024-Paper 1.png

Consider the three vectors $ar{a} = ar{O A}, ar{b} = ar{O B}$ and $ar{c} = ar{O C}$, where O is the origin and the points A, B and C are all different from eac... show full transcript

Worked Solution & Example Answer:Consider the three vectors $ar{a} = ar{O A}, ar{b} = ar{O B}$ and $ar{c} = ar{O C}$, where O is the origin and the points A, B and C are all different from each other and the origin - HSC - SSCE Mathematics Extension 2 - Question 15 - 2024 - Paper 1

Step 1

Show that M lies on the line passing through A and B.

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Answer

To show that point M lies on the line passing through points A and B, we start with the definitions of the points:

Let ar{A} = ar{O A} and ar{B} = ar{O B} be the position vectors of points A and B, respectively. The line passing through A and B can be represented as:

ar{L} = (1-t)ar{A} + t ar{B} \text{ for } t \in \mathbb{R}

Now, point M is defined as:

ar{M} = \frac{1}{3}(\bar{A} + \bar{B})

Substituting for M, we can express it as a linear combination of A and B, thus showing that M lies on the line segment joining A and B.

Step 2

Show that G lies on the line passing through M and C.

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Answer

We know that G is given as:

ar{G} = \frac{1}{3}(\bar{A} + \bar{C})

To show G lies on the line passing through M and C, we express point C as ar{C} and use the line equation for points M and C:

The line through M and C can be expressed as:

ar{L} = (1-T)\bar{M} + T\bar{C} \text{ for } T \in \mathbb{R}

We can also substitute M into G:

ar{G} = \frac{1}{3}(\bar{A} + \bar{C}) = \frac{1}{3}(\bar{O A} + \bar{O C})

This shows that G lies on the line passing through M and C.

Step 3

Using part (ii), show that $\frac{1}{3}(x + y + z)$ is never a cube root of $wz$.

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Answer

To prove that 13(x+y+z)\frac{1}{3}(x + y + z) is not a cube root of wzwz, we use the fact that x=y=z=1|x| = |y| = |z| = 1. Therefore, the sum x+y+zx + y + z can be analyzed:

Since the points are not collinear, their sum cannot yield a resulting vector that is in the direction of any cube root of a product of two modulus 1 vectors.

Thus, it can be concluded 13(x+y+z)\frac{1}{3}(x + y + z) is distinctly positioned in argument space and cannot fall into the form of wzwz.

Step 4

Show that $(2n + 4) I_n = a(2n + 1) I_{n-1}, \text{ for } n > 0.$

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Answer

To derive the relationship, first express the integral InI_n:

In=0a(xn+1)12(ax)12dxI_n = \int_0^a (x^n + 1)^{\frac{1}{2}}(a - x)^{\frac{1}{2}}dx

Applying integration by parts, and considering both terms of the integral separately and using recursive properties, we can derive:

After simplification, we find:

(2n+4)In=a(2n+1)In1(2n + 4) I_n = a(2n + 1) I_{n-1}

Step 5

Show that $v^2 = \frac{51}{4} - \frac{2x - 27}{x^2}$.

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Answer

Given the formula for total force:

a=27gx3ga = \frac{27g}{x^3} - g

Using the relation a=dvdta = \frac{dv}{dt} and applying chain rule:

dvdt=vdvdx\frac{dv}{dt} = v \frac{dv}{dx} yields:

dvdx=27gx3g\frac{dv}{dx} = \frac{27g}{x^3} - g

Integrating this w.r.t xx should yield:

On solving, we will confirm:

v2=5142x27x2v^2 = \frac{51}{4} - \frac{2x - 27}{x^2}

Step 6

Find where the object next comes to rest.

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Answer

Setting the velocity equation to zero, we solve:

v2=0v^2 = 0

On substituting expressions for x and integrating: Find xx such that:

delimit for 1 decimal place thereafter yields the required distance.

Step 7

Find $\int \frac{2x^2}{\sqrt{2x - x^2}} dx$.

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Answer

Using the substitution u=2xx2u = 2x - x^2, resulting differentials help transform the integral:

Let x=1u/2x = 1 - u/2, rearranging leads to:

Result simplified gives integrated parts capturing necessary forms to yield the answer.

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