Mathematical Methods
Group-B
Short Answer Questions

24) Find the derivative of [tex] f(x)=\left(6 x^4+2 x^3\right)\left(5 x-10 x^2+18 x^5-4\right) [/tex]

Solution:

Given function:
[tex] f(x)=\left(6 x^4+2 x^3\right)\left(5 x-10 x^2+18 x^5-4\right) [/tex]

The derivative of the given function can be found as:
[tex]
\begin{aligned}
f'(x) & = \frac{d}{d x}\left[\left(6 x^4+2 x^3\right)\left(5 x-10 x^2+18 x^5-4\right)\right] \\
& = \left(6 x^4+2 x^3\right) \frac{d}{d x}\left(5 x-10 x^2+18 x^5-4\right) + \left(5 x-10 x^2+18 x^5-4\right) \frac{d}{d x}\left(6 x^4+2 x^3\right)
\end{aligned}
[/tex]



Answer :

To find the derivative of [tex]\( f(x) = (6 x^4 + 2 x^3)(5 x - 10 x^2 + 18 x^5 - 4) \)[/tex], we will use the product rule of differentiation. The product rule states that if we have two functions [tex]\( u(x) \)[/tex] and [tex]\( v(x) \)[/tex], then the derivative of their product is given by:

[tex]\[ (u(x) \cdot v(x))' = u'(x) \cdot v(x) + u(x) \cdot v'(x) \][/tex]

Let's denote:
[tex]\[ u(x) = 6 x^4 + 2 x^3 \][/tex]
[tex]\[ v(x) = 5 x - 10 x^2 + 18 x^5 - 4 \][/tex]

First, we need to find the derivatives of [tex]\( u(x) \)[/tex] and [tex]\( v(x) \)[/tex].

### Step 1: Find [tex]\( u'(x) \)[/tex]
[tex]\[ u(x) = 6 x^4 + 2 x^3 \][/tex]
Differentiating [tex]\( u(x) \)[/tex] with respect to [tex]\( x \)[/tex]:
[tex]\[ u'(x) = \frac{d}{d x}(6 x^4) + \frac{d}{d x}(2 x^3) \][/tex]
[tex]\[ u'(x) = 24 x^3 + 6 x^2 \][/tex]

### Step 2: Find [tex]\( v'(x) \)[/tex]
[tex]\[ v(x) = 5 x - 10 x^2 + 18 x^5 - 4 \][/tex]
Differentiating [tex]\( v(x) \)[/tex] with respect to [tex]\( x \)[/tex]:
[tex]\[ v'(x) = \frac{d}{d x}(5 x) + \frac{d}{d x}(-10 x^2) + \frac{d}{d x}(18 x^5) + \frac{d}{d x}(-4) \][/tex]
[tex]\[ v'(x) = 5 - 20 x + 90 x^4 \][/tex]

### Step 3: Apply the Product Rule
Using the product rule, we have:
[tex]\[ f'(x) = u'(x) \cdot v(x) + u(x) \cdot v'(x) \][/tex]
Substituting [tex]\( u(x) \)[/tex], [tex]\( u'(x) \)[/tex], [tex]\( v(x) \)[/tex], and [tex]\( v'(x) \)[/tex]:
[tex]\[ f'(x) = (24 x^3 + 6 x^2)(5 x - 10 x^2 + 18 x^5 - 4) + (6 x^4 + 2 x^3)(5 - 20 x + 90 x^4) \][/tex]

### Conclusion:
Therefore, the derivative of the given function is:
[tex]\[ f'(x) = (24 x^3 + 6 x^2)(5 x - 10 x^2 + 18 x^5 - 4) + (6 x^4 + 2 x^3)(5 - 20 x + 90 x^4) \][/tex]

This is the step-by-step solution to finding the derivative of the function [tex]\( f(x) \)[/tex].