The equation $4k^3 - 27k + k = 0$ has a double root - HSC - SSCE Mathematics Extension 2 - Question 5 - 2002 - Paper 1
Question 5
The equation $4k^3 - 27k + k = 0$ has a double root. Find the possible values of $k$.
Let $\alpha, \beta$ and $\gamma$ be the roots of the equation $x^3 - 5x^2 + 5 ... show full transcript
Worked Solution & Example Answer:The equation $4k^3 - 27k + k = 0$ has a double root - HSC - SSCE Mathematics Extension 2 - Question 5 - 2002 - Paper 1
Step 1
Find the possible values of k.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To find the possible values of k for which the equation 4k3−27k+k=0 has a double root, we can rewrite the equation as:
4k3−27k=0
Factoring gives:
k(4k2−27)=0,
Thus, k=0 or 4k2−27=0. Solving for k yields:
k = \pm\frac{3\sqrt{3}}{2}.$$
Step 2
Find a polynomial equation with integer coefficients whose roots are \alpha - 1, \beta - 1, and \gamma - 1.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Given that the polynomial is P(x)=x3−5x2+5. To find the roots α−1,β−1,γ−1, we substitute:
Q(x)=P(x+1)=(x+1)3−5(x+1)2+5.
Expanding this gives:
Q(x)=x3+3x2+3x+1−5(x2+2x+1)+5=x3−2x+1.
Step 3
Find a polynomial equation with integer coefficients whose roots are \alpha^2, \beta^2, and \gamma^2.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Using the previously found polynomial P(x), we can find the roots. The required polynomial can be derived from:
R(x)=P(x)P(−x).
This results in:
R(x)=(x3−5x3/2+5)(x3+5x3/2+5),
leading us to the required polynomial with integer coefficients after simplification.
Step 4
Find the value of \alpha^3 + \beta^3 + \gamma^3.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Using the property of polynomial roots:
α3+β3+γ3=(α+β+γ)(α2+β2+γ2−αβ−βγ−γα)+3αβγ.
Show that the equation of the tangent to the ellipse at the point P(x_1, y_1) is \frac{x_1 x}{a^2} + \frac{y_1 y}{b^2} = 1.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To find the equation of the tangent to the ellipse at point P(x1,y1), we use the standard form of the tangent line in ellipses. The derived equation is:
a2x1x+b2y1y=1.
This utilizes the point-slope form tangent to an ellipse.
Step 6
Show that the equation of the chord of contact from T is \frac{x_0 x}{a^2} + \frac{y_0 y}{b^2} = 1.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To derive the chord of contact from the point T(x0,y0) to the ellipse, we apply the standard form given the coordinates. The resulting equation is:
a2x0x+b2y0y=1,
which represents the line connecting point T to the ellipse.