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Wednesday, February 16, 2011

Q.306. To find equation of the parabola given conditions

Question 306.
Find the equation of the parabola with the vertical axis that passes through the point (0,2) and the points of intersection of the parabolas x^2+2x+3y+4=0 and x^2-3x+y+3=0.

Answer 306.
Equation of a parabola passing through the points of intersection of the parabolas
x^2 + 2x + 3y + 4 = 0 and x^2 - 3x + y + 3 = 0 is given by
x^2 + 2x + 3y + 4 + k (x^2 - 3x + y + 3) = 0 ... (1)
As it passes through (0, 2),
0 + 0 + 3*2 + 4 + k (0 - 0 + 2 + 3) = 0
=> k = - 2
Plugging the value of k = - 2 in (1),
the equation of the required parabola is
x^2 + 2x + 3y + 4 - 2 (x^2 - 3x + y + 3) = 0
=> x^2 - 8x - y + 2 = 0.

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