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The point A has position vector $egin{pmatrix} 8 \ -6 \ 5 \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \\ \ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \ \\ \\ \ 6 \\ \ \\ \ \\ 125 \\ \\ \ \\ \\ \ \\ \\ \ \\ \\ \ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8 \\ \ \ 10 \\ 10 \\10 \\-10 \\ 6 \\ -10 \\ \ \ \ \ \ \ \ \ \ \ \ \ \ 10 \\ \ 5 -6 \ \\ \\ 5 \\ \ \ \ \ \ \ \ - \\ 0\\ -1\\ 4 \\ \ \ \ \ \ \ 4 \\ \ \ \ \ \ \ 5 \\ \ 4 \\ -0\\ \\ -6 \\ -8 \\ \\ \\ \ \ \ \ * 25 \\ \ 12 \ 1 -0 -0 \ 5 +10 +10 +5 \ \ 0 0 + 1 + 1 + 0$ The line $egin{pmatrix} x \ y \ z \\ \ \\ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \ 0 \\ -6 \\ 7 \\ 5 \ 1\ \ \ \ \ \ 1 12 \ 40\ 4\ \ 2 7 - - - -7 -2 7 -100 \ \\ \ \ \ \ \ \ \ \ \ -15-3 \ 17 +6 +6 +60 \\ 20 -0 10 0\ 31 10 \ \\ \ 0 -30 \\ \ \ \ \ \ \ \ \ 10 \\ \ 5 \\ The point B lies on $ ext{l}$ and has position vector $egin{pmatrix} p \ 1 \ 2 p \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ \ \ -\ 0 \\ 2 \ \ \ \ \ \ 2 + 10 \ \ \ 7 \ \\ 2 \ \ \ +2 12 \ \ \ 5 \ \ \ + 8\ 0 \ \ \ \ \ \ \ 0 \ \ \ \ \ \10 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ 0 \ 6+12-25-8-0-0 \ 1 \ \ \ \ \ +12 - \ 2 \-0 \\ -0\ \ 0 \ \ \ \ 6 +40 -6 +6 -10 -0 -80 -100 \ 46 +5 \ \ \ \ \ +100 -10 8 0 +25 +20 \\ \ \ \ \ -0\ 4 +4 -4 -20 + 2 + 12 +12 - 10 + 10 +10 +40 +45 +30 +30 +20 +40 +8 +100$ - HSC - SSCE Mathematics Extension 2 - Question 13 - 2024 - Paper 1

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Question 13

The-point-A-has-position-vector-$egin{pmatrix}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he-line-$egin{pmatrix}-x-\-y-\-z-\\-\-\\-\\-\--\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\\-\-0-\\--6-\\-7-\\-5-\-1\-\-\-\-\-\-1-12-\-40\-4\-\-2-7--------7---2--7----100---\--\\-\-\-\-\-\-\-\-\-\--15-3-\-17-+6-+6-+60-\\-20--0-10-0\-31-10--\-\\--\-0--30-\\-\-\-\-\-\-\-\--\-10-\\-\-5-\\--The-point-B-lies-on-$-ext{l}$-and-has-position-vector-$egin{pmatrix}-p-\-1-\-2-p-\\--\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-0-\-\-\--\-0-\\-2-\-\-\-\-\-\-2-+-10-\-\-\-7-\-\\--2-\-\-\-+2-12-\-\-\-5-\-\-\-+-8\-0-\-\-\-\-\-\--\-0-\-\-\-\-\--\10-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-0-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\----\\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-0---\-0--\-6+12-25-8-0-0-\-1-\-\-\-\-\-+12---\-2-\-0-\\--0\-\-0-\-\-\-\-6-+40--6-+6--10--0--80---100-\-46-+5-\-\-\-\-\-+100--10-8-0-+25-+20-\\-\-\-\-\---0\-4-+4--4--20-+-2-+-12-+12---10-+-10-+10-+40-+45-+30-+30-+20-+40-+8-+100$-HSC-SSCE Mathematics Extension 2-Question 13-2024-Paper 1.png

The point A has position vector $egin{pmatrix} 8 \ -6 \ 5 \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \... show full transcript

Worked Solution & Example Answer:The point A has position vector $egin{pmatrix} 8 \ -6 \ 5 \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \\ \ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \ \\ \\ \ \\ \\ \ 6 \\ \ \\ \ \\ 125 \\ \\ \ \\ \\ \ \\ \\ \ \\ \\ \ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8 \\ \ \ 10 \\ 10 \\10 \\-10 \\ 6 \\ -10 \\ \ \ \ \ \ \ \ \ \ \ \ \ \ 10 \\ \ 5 -6 \ \\ \\ 5 \\ \ \ \ \ \ \ \ - \\ 0\\ -1\\ 4 \\ \ \ \ \ \ \ 4 \\ \ \ \ \ \ \ 5 \\ \ 4 \\ -0\\ \\ -6 \\ -8 \\ \\ \\ \ \ \ \ * 25 \\ \ 12 \ 1 -0 -0 \ 5 +10 +10 +5 \ \ 0 0 + 1 + 1 + 0$ The line $egin{pmatrix} x \ y \ z \\ \ \\ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \ 0 \\ -6 \\ 7 \\ 5 \ 1\ \ \ \ \ \ 1 12 \ 40\ 4\ \ 2 7 - - - -7 -2 7 -100 \ \\ \ \ \ \ \ \ \ \ \ -15-3 \ 17 +6 +6 +60 \\ 20 -0 10 0\ 31 10 \ \\ \ 0 -30 \\ \ \ \ \ \ \ \ \ 10 \\ \ 5 \\ The point B lies on $ ext{l}$ and has position vector $egin{pmatrix} p \ 1 \ 2 p \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ \ \ -\ 0 \\ 2 \ \ \ \ \ \ 2 + 10 \ \ \ 7 \ \\ 2 \ \ \ +2 12 \ \ \ 5 \ \ \ + 8\ 0 \ \ \ \ \ \ \ 0 \ \ \ \ \ \10 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ 0 \ 6+12-25-8-0-0 \ 1 \ \ \ \ \ +12 - \ 2 \-0 \\ -0\ \ 0 \ \ \ \ 6 +40 -6 +6 -10 -0 -80 -100 \ 46 +5 \ \ \ \ \ +100 -10 8 0 +25 +20 \\ \ \ \ \ -0\ 4 +4 -4 -20 + 2 + 12 +12 - 10 + 10 +10 +40 +45 +30 +30 +20 +40 +8 +100$ - HSC - SSCE Mathematics Extension 2 - Question 13 - 2024 - Paper 1

Step 1

Show that $|AB|^2 = 6p^2 - 24p + 125$

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114 rated

Answer

To find the distance squared AB2|AB|^2, we begin with the position vectors of A and B:

AB2=BA2=(p,1,2p)(8,6,5)2|AB|^2 = |B - A|^2 = |(p, 1, 2p) - (8, -6, 5)|^2

Calculating this gives:

AB2=(p8,1+6,2p5)2=(p8)2+(7)2+(2p5)2|AB|^2 = |(p - 8, 1 + 6, 2p - 5)|^2 = (p - 8)^2 + (7)^2 + (2p - 5)^2

Expanding this:

(p8)2=p216p+64(p - 8)^2 = p^2 - 16p + 64

(2p5)2=4p220p+25(2p - 5)^2 = 4p^2 - 20p + 25

Combining these:

AB2=p216p+64+49+4p220p+25|AB|^2 = p^2 - 16p + 64 + 49 + 4p^2 - 20p + 25

This simplifies to:

6p236p+138=6p224p+1256p^2 - 36p + 138 = 6p^2 - 24p + 125

Step 2

Hence, or otherwise, determine the shortest distance between the point A and the line $ ext{l}$.

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Answer

To minimize the distance, we differentiate AB2|AB|^2 with respect to pp:

rac{d(|AB|^2)}{dp} = 12p - 24

Setting this to zero to find critical points:

12p24=0p=212p - 24 = 0 \\ p = 2

Now substituting p=2p = 2 back into AB2|AB|^2:

AB2=6(2)224(2)+125=49|AB|^2 = 6(2)^2 - 24(2) + 125 = 49

Thus, the shortest distance is:

extDistance=extsqrt(49)=7 ext{Distance} = ext{sqrt}(49) = 7

Step 3

A particle is moving in simple harmonic motion, described by $x = -4(t + 1)$.

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Answer

Given the position function, we can find the speed:

v = rac{dx}{dt} = -4

When the particle passes the origin, we set x=0x = 0 and solve for time:

0=4(t+1)t=10 = -4(t + 1) \\ t = -1

The speed at this point is given as 4 m/s. The distance travelled in one complete cycle is:

extDistance=(t)=4imes2=8extmeters ext{Distance} = |(-t)| = |-4| imes 2 = 8 ext{ meters}

Step 4

A particle of unit mass moves horizontally in a straight line. It experiences a resistive force proportional to $v^2$, where $v$ ms$^{-1}$ is the speed of the particle, so that the acceleration is given by $a = -kv^2$.

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Answer

Starting with:

rac{dv}{dt} = -kv^2 \\ ext{We can separate variables:} \\ rac{1}{v^2} dv = -k dt

Integrating:

rac{-1}{v} = kt + C \\ v = rac{1}{kt + C}

Substituting initial conditions to find C and k: v(0) = 40 ext{ gives us } 40 = rac{1}{C} \\ C = rac{1}{40} By substituting into the equation, we get: v = rac{40}{kt + rac{1}{40}}

To determine when the velocity is 30 m/s to the right:

40=30(k(t40))kt=1540 = 30(k(t - 40)) \\ kt = 15

Step 5

It is known that for all positive real numbers x, y, $x + y ≥ 2 ext{sqrt}(xy)$.

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Answer

To prove this, we apply the AM-GM inequality:

rac{x + y}{2} ≥ ext{sqrt}(xy)

This gives: x+y2extsqrt(xy)x + y ≥ 2 ext{sqrt}(xy)

This establishes the relationship for all positive real numbers.

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