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taurus [48]
2 years ago
9

Suppose that y = k * (x - 1/3) ^ 2 is a parabola in the xy -plane that passes through the point (2/3, 1) :Find k and the length

of the horizontal chord of the parabola that has one end at (2/3, 1) .
Mathematics
1 answer:
Dennis_Churaev [7]2 years ago
6 0

Answer:

k = 9

length of chord = 2/3

Step-by-step explanation:

Equation of parabola:   y=k (x-\frac13)^2

<u />

<u>Part 1</u>

If the curve passes through point (\frac23 ,1), this means that when x=\dfrac23, y = 1

Substitute these values into the equation and solve for k:

\implies 1=k \left(\dfrac23-\dfrac13\right)^2

\implies 1=k \left(\dfrac13 \right)^2

Apply the exponent rule \left(\dfrac{a}{b} \right)^c=\dfrac{a^c}{b^c} :

\implies 1=k \left(\dfrac{1^2}{3^2} \right)

\implies 1=\dfrac{1}{9}k

\implies k=9

<u>Part 2</u>

  • The chord of a parabola is a line segment whose endpoints are points on the parabola.  

We are told that one end of the chord is at (\frac23 ,1) and that the chord is horizontal.  Therefore, the y-coordinate of the other end of the chord will also be 1.  Substitute y = 1  into the equation for the parabola and solve for x:

\implies 1=9 \left(x-\dfrac13 \right)^2

\implies \dfrac19 = \left(x-\dfrac13 \right)^2

\implies \sqrt{\dfrac19}  = x-\dfrac13

\implies \pm \dfrac13  = x-\dfrac13

\implies x=\dfrac23, x=0

Therefore, the endpoints of the horizontal chord are: (0, 1) and (2/3, 1)

To calculate the length of the chord, find the difference between the x-coordinates:  

\implies \dfrac23-0=\dfrac23

**Please see attached diagram for drawn graph. Chord is in red**

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