Find the point on the curve y2 = 4x which is nearest to the point (2, –8).
Given Curve is y2 = 4x …… (1)
Let us assume the point on the curve which is nearest to the point (2, - 8) be (x, y)
The (x, y) satisfies the relation(1)
Let us find the distance(S) between the points (x, y) and (2, - 8)
We know that distance between two points (x1,y1) and (x2,y2) is .
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Squaring on both sides we get,
⇒ S2 = x2 + y2 - 4x + 16y + 68
From (1)
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We know that distance is an positive number so, for a minimum distance S, S2 will also be minimum
Let us S2 as the function of y.
For maxima and minima,
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⇒ y3 - 64 = 0
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On solving we get
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Now differentiating again
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At y = 4
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We get minimum distance at y = 4
Let find the value of x at these y values
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⇒ x = 4
∴ The nearest point to the point (2, - 8) on the curve is (4,4).