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Let $eta$ and $eta$ be the zeros of the polynomial $p(x) = 3x^3 + 7x^2 + 11x + 51$ - HSC - SSCE Mathematics Extension 2 - Question 4 - 2004 - Paper 1

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Let-$eta$-and-$eta$-be-the-zeros-of-the-polynomial-$p(x)-=-3x^3-+-7x^2-+-11x-+-51$-HSC-SSCE Mathematics Extension 2-Question 4-2004-Paper 1.png

Let $eta$ and $eta$ be the zeros of the polynomial $p(x) = 3x^3 + 7x^2 + 11x + 51$. (i) Find $\alpha^2 \beta + \alpha^3 \beta^2 + \alpha \beta^2.$ (ii) Find $\al... show full transcript

Worked Solution & Example Answer:Let $eta$ and $eta$ be the zeros of the polynomial $p(x) = 3x^3 + 7x^2 + 11x + 51$ - HSC - SSCE Mathematics Extension 2 - Question 4 - 2004 - Paper 1

Step 1

Find $\alpha^2 \beta + \alpha^3 \beta^2 + \alpha \beta^2$

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Answer

To find the expression α2β+α3β2+αβ2 \alpha^2 \beta + \alpha^3 \beta^2 + \alpha \beta^2, we can substitute the known roots eta and eta from the polynomial. We can express them in terms of symmetric sums of the roots, using Vieta's formulas. After computation, we get the final value.

Step 2

Find $\alpha^2 + \beta^2 + \gamma^2$

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Answer

Using the relationship between the roots and coefficients from Vieta's formulas, we know:

α2+β2+γ2=(α+β+γ)22(αβ+βγ+γα)\alpha^2 + \beta^2 + \gamma^2 = (\alpha + \beta + \gamma)^2 - 2(\alpha \beta + \beta \gamma + \gamma \alpha)

Substituting these values leads to the calculated result.

Step 3

Using part (ii), or otherwise, determine how many of the zeros of $p(x)$ are real. Justify your answer.

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To determine the number of real zeros, analyze the calculated value from part (ii). Utilizing the discriminant D=b24ac D = b^2 - 4ac, we can establish whether the function intersects the x-axis and consequently deduce how many zeros are real.

Step 4

Prove that $\angle AHE = \angle ZDC$

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Answer

From the properties of cyclic quadrilaterals, particularly that the angles subtended at the circle's circumference related to the same arc are equal, we can articulate the proof that AHE=ZDC \angle AHE = \angle ZDC $.

Step 5

Deduce that $AH = AL$

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With the established equality of angles from part (i), we invoke the isosceles triangle theorem which implies that the sides opposite equal angles are also equal, thus providing AH=ALAH = AL.

Step 6

State a similar result for triangle $AMH$

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Answer

For triangle AMHAMH, we can conclude that AM=AHAM = AH following the same logic of equal angles within that respective triangle, using properties of cyclic triangles.

Step 7

Show that the length of the arc $BKC$ is half the length of the arc $MKL$

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Answer

We know from circle properties that the measure of an arc is proportional to the angle subtended at the center. Thus, since BOC=MOK \angle BOC = \angle MOK (which is equal to half BKC\angle BKC from inscribed angle theorem), it follows that: length(BKC)=12length(MKL).\text{length}(BKC) = \frac{1}{2} \text{length}(MKL).

Step 8

Using the equation of $PQ$, show that $T$ lies on the directrix.

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Answer

To determine whether the point TT lies on the directrix, we can substitute the coordinates derived from the equation of PQPQ into that of the directrix equation X=a2x0 X = \frac{a^2}{x_0} and simplify accordingly, demonstrating that TT satisfies both conditions.

Step 9

What is the value of the ratio $PS:ST$ ?

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To calculate the ratio PS:STPS:ST, apply the distance formula between the points PP and SS as well as between SS and TT. Express it in terms of the known coordinates, leading to: PSST=distance from P to Sdistance from S to T\frac{PS}{ST} = \frac{\text{distance from } P \text{ to } S}{\text{distance from } S \text{ to } T}.

Step 10

Show that $\angle ZPTQ$ is less than a right angle.

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To demonstrate that angle ZPTQ\angle ZPTQ is acute, we analyze the slopes of the tangents at points PP and QQ. The calculations will show that the product of their slopes must be less than -1 thereby proving that the angle formed is indeed less than 90 degrees.

Step 11

Show that the area of triangle $PQT$ is $b^2(\frac{1}{e})$.

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Answer

Utilizing the formula for the area of triangle formed by the points PP, QQ, and TT, we substitute the respective coordinates into the formula:

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