Find the point on the curve 2a2y = x3 – 3ax2 where the tangent is parallel to the x – axis.
Given:
The curve is 2a2y = x3 – 3ax2
Differentiating the above w.r.t x
⇒ 2a2 = 3x3 – 1 – 3
2ax2 – 1
⇒ 2a2 = 3x2 – 6ax
⇒ =
...(1)
= The Slope of the tangent = tan
Since, the tangent is parallel to x – axis
i.e,
⇒ = tan(0) = 0 ...(2)
tan(0) = 0
= The Slope of the tangent = tan
From (1) & (2),we get,
⇒ = 0
⇒ 3x2 – 6ax = 0
⇒ 3x(x – 2a) = 0
⇒ 3x = 0 or (x – 2a) = 0
⇒ x = 0 or x = 2a
Substituting x = 0 or x = 2a in 2a2y = x3 – 3ax2,
when x = 0
⇒ 2a2y = (0)3 – 3a(0)2
⇒ y = 0
when x = 2
⇒ 2a2y = (2a)3 – 3a(2a)2
⇒ 2a2y = 8a3 – 12a3
⇒ 2a2y = – 4a3
⇒ y = – 2a
Thus, the required point is (0,0) & (2a, – 2a)