Let f : (0, ∞ ) →R be a differentiable function such that ...
Given Information
The function f : (0,∞) → R is differentiable.
f(x^2) = 1 - x^3 for all x > 0
f(1) = 0
Solution
We need to find the value of f(4).
Step 1: Differentiating the given equation
Let's differentiate the given equation f(x^2) = 1 - x^3 with respect to x.
Using the chain rule, we have:
2x * f'(x^2) = -3x^2
Simplifying the equation, we get:
f'(x^2) = -3x / (2x)
Simplifying further, we have:
f'(x^2) = -3/2
Step 2: Finding the derivative of f(x)
To find the derivative of f(x), we substitute x^2 with x in the derivative we obtained in Step 1.
f'(x) = -3 / (2√x)
Step 3: Integrating the derivative to find f(x)
Integrating f'(x) with respect to x, we obtain f(x):
f(x) = -3 / 2 * ∫ (1 / √x) dx
Integrating, we get:
f(x) = -3 / 2 * 2√x + C
Simplifying further, we have:
f(x) = -3√x + C
Step 4: Finding the value of C
Using the given condition f(1) = 0, we substitute x = 1 into the equation f(x) = -3√x + C.
0 = -3√1 + C
0 = -3 + C
C = 3
Step 5: Finding f(4)
Substituting x = 4 into the equation f(x) = -3√x + C, we have:
f(4) = -3√4 + 3
f(4) = -3 * 2 + 3
f(4) = -6 + 3
f(4) = -3
Thus, the value of f(4) is -3, which is not listed as one of the given options. Therefore, the given answer options seem to be incorrect.
Please note that option 'A' (-47/5) is not the correct answer based on the given information.