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
Question 4
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
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Answer
To find the expression α2β+α3β2+αβ2, 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)2−2(αβ+βγ+γα)
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=b2−4ac, 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 $.
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=AL.
Step 6
State a similar result for triangle $AMH$
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For triangle AMH, we can conclude that AM=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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We know from circle properties that the measure of an arc is proportional to the angle subtended at the center. Thus, since ∠BOC=∠MOK (which is equal to half ∠BKC from inscribed angle theorem), it follows that:
length(BKC)=21length(MKL).
Step 8
Using the equation of $PQ$, show that $T$ lies on the directrix.
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To determine whether the point T lies on the directrix, we can substitute the coordinates derived from the equation of PQ into that of the directrix equation X=x0a2 and simplify accordingly, demonstrating that T satisfies both conditions.
Step 9
What is the value of the ratio $PS:ST$ ?
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To calculate the ratio PS:ST, apply the distance formula between the points P and S as well as between S and T. Express it in terms of the known coordinates, leading to:
STPS=distance from S to Tdistance from P to S.
Step 10
Show that $\angle ZPTQ$ is less than a right angle.
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To demonstrate that angle ∠ZPTQ is acute, we analyze the slopes of the tangents at points P and Q. 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 P, Q, and T, we substitute the respective coordinates into the formula: