Find the equation of each normal of the function f(x) = 1/3 * x ^ 3 + x ^ 2 + x - 1/8 which is parallel to the line

y=- 1 4 x+ 1 3 .

3 answers

First, find the derivative of the function f(x):

f'(x) = x^2 + 2x + 1

Since we are looking for a line parallel to y = -14x + 13, the slope of the normal line must also be -14.

The slope of the normal line can be found using the derivative:

f'(x) = -1/14

Solving for x:

x^2 + 2x + 1 = -1/14

Multiplying by 14 to clear fractions:

14x^2 + 28x + 14 = -1

Subtracting 14 from both sides:

14x^2 + 28x + 15 = 0

Using the quadratic formula:

x = (-28 ± sqrt(28^2 - 4(14)(15))) / (2(14))

x = (-28 ± 2sqrt(37)) / 28

Simplifying:

x = (-1 ± sqrt(37)) / 2

These are the x-coordinates of the points where the normal lines intersect with the graph of f(x).

To find the corresponding y-coordinates, plug these values of x into f(x):

y = (1/3)(-1 ± sqrt(37))^3 + (-1 ± sqrt(37))^2 + (-1 ± sqrt(37)) - 1/8

Therefore, the equations of the normal lines are:

y = -14x + (117 ± 56sqrt(37)) / 28

Simplifying:

y = -7/2x + (117 ± 56sqrt(37)) / 28

The two normal lines are:

y = -7/2x + (117 + 56sqrt(37)) / 28

y = -7/2x + (117 - 56sqrt(37)) / 28
AAAaannndd the bot gets it wrong yet again!
x^2 + 2x + 1 = -1/14
(x+1)^2 = -1/14
There are no real solutions to this, since a square cannot be negative.

Of course, since the tangent line must be parallel to y = -14x+13, the slope of the normal is 1/14.
x^2 + x + 1 = 1/14
x = -1 ± 1/√14
You are correct. I apologize for the mistake in my previous response. Thank you for providing the correct solution.