from a handpicked tutor in LIVE 1-to-1 classes
Find the point p on the parabola y = x2 closest to the point (3, 0).
Solution:
Given, the equation of parabola is y = x2
We have to find the point p on the parabola closest to the point (3, 0).
Let (x,y) be the point closest to the point (3, 0).
Using distance formula,
D = \(\sqrt{(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}}\)
D = \(\sqrt{xt-3)^{2}+(y-0)^{2}}\)
D = \(\sqrt{(x-3)^{2}+(y)^{2}}\)
D = \(\sqrt{(x^{2}+9-6x+y^{2})}\)
Now substituting the value of y in the above equation,
D = \(\sqrt{(x^{2}+9-6x+(x^{2})^{2})}\)
\(D =\sqrt{(x^{2}+9-6x+x^{4})}\)
Differentiating with respect to x,
dD/dx = 4x3 + 2x - 6
To find the value of x, let dD/dx = 0
4x3 + 2x - 6 = 0
Dividing by 2 on both sides,
2x3 + x - 3 = 0
On solving,
2x3 - 2x2 + 2x2 - 2x + 3x - 3 = 0
2x2(x - 1) + 2x(x - 1) + 3(x - 1) = 0
(x - 1)(2x2 + 2x + 3) = 0
x - 1 = 0
x = 1
2x2 + 2x + 3 ≠ 0
Second derivative,
d2D/dx2 = 12x2 + 2
12x2 + 2 = 0
At x = 1,
d2D/dx2 > 0
So, at x = 1, D is minimum.
Put the value of x in the equation of parabola,
So, y = (1)2
y = 1
Therefore, the point p is (1,1)
Find the point p on the parabola y = x2 closest to the point (3, 0).
Summary:
The point p on the parabola y = x2 closest to the point (3, 0) is (1,1).
visual curriculum