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Question
Find the equation of the parabola which is symmetrical about x-axis and passing through (–2, –3).
Solution
Equation of the parabola symmetrical about X-axis is either y2 = 4ax or y2 = - 4ax.
Since the parabola passes through (-2, -3) it will be of the form y2 = - 4ax ...(1)
Substituting (-2, -3) in (1) we get,
y2 = - 4ax
(-3)2 = - 4a(-2)
⇒ 9 = 8a
⇒ a = `9/8`
Substituting a = `9/8` in (1) we get,
y2 = - 4ax
y2 = - 4`(9/8)`x
⇒ y2 = `(-9)/2`x
which is required equation of the parabola.
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