If [tex]\( h(x) = \sqrt{4 + 3 f(x)} \)[/tex], where [tex]\( f(4) = 4 \)[/tex] and [tex]\( f^{\prime}(4) = 3 \)[/tex], find [tex]\( h^{\prime}(4) \)[/tex].

[tex]\[ h^{\prime}(4) = \quad \][/tex]



Answer :

To find [tex]\( h'(4) \)[/tex] given [tex]\( h(x) = \sqrt{4 + 3f(x)} \)[/tex], where [tex]\( f(4) = 4 \)[/tex] and [tex]\( f'(4) = 3 \)[/tex], let's perform the following steps:

1. Differentiate [tex]\( h(x) \)[/tex] with respect to [tex]\( x \)[/tex]:

Given [tex]\( h(x) = \sqrt{4 + 3f(x)} \)[/tex], we need to differentiate this with respect to [tex]\( x \)[/tex].

First, let's set:
[tex]\[ u = 4 + 3f(x) \][/tex]

Thus, [tex]\( h(x) = \sqrt{u} \)[/tex].

The derivative [tex]\( h'(x) \)[/tex] can be found using the chain rule. We first differentiate [tex]\( \sqrt{u} \)[/tex] with respect to [tex]\( u \)[/tex] and then multiply by the derivative of [tex]\( u \)[/tex] with respect to [tex]\( x \)[/tex]:
[tex]\[ \frac{d}{dx} \sqrt{u} = \frac{1}{2\sqrt{u}} \cdot \frac{du}{dx} \][/tex]

2. Differentiate [tex]\( u \)[/tex] with respect to [tex]\( x \)[/tex]:

Recall that:
[tex]\[ u = 4 + 3f(x) \][/tex]

Therefore:
[tex]\[ \frac{du}{dx} = 3 \frac{df(x)}{dx} = 3f'(x) \][/tex]

Now, we have:
[tex]\[ \frac{d}{dx} \sqrt{4 + 3f(x)} = \frac{1}{2\sqrt{4 + 3f(x)}} \cdot 3f'(x) \][/tex]

Simplifying:
[tex]\[ h'(x) = \frac{3f'(x)}{2\sqrt{4 + 3f(x)}} \][/tex]

3. Evaluate [tex]\( h'(x) \)[/tex] at [tex]\( x = 4 \)[/tex]:

We are given [tex]\( f(4) = 4 \)[/tex] and [tex]\( f'(4) = 3 \)[/tex]. Substitute these values into the expression for [tex]\( h'(x) \)[/tex]:

[tex]\[ h'(4) = \frac{3 f'(4)}{2\sqrt{4 + 3 f(4)}} \][/tex]

Substitute [tex]\( f(4) = 4 \)[/tex] and [tex]\( f'(4) = 3 \)[/tex]:

[tex]\[ h'(4) = \frac{3 \cdot 3}{2\sqrt{4 + 3 \cdot 4}} \][/tex]

Simplify inside the square root:

[tex]\[ 4 + 3 \cdot 4 = 4 + 12 = 16 \][/tex]

Thus:

[tex]\[ h'(4) = \frac{9}{2 \cdot \sqrt{16}} = \frac{9}{2 \cdot 4} = \frac{9}{8} \][/tex]

Therefore, the derivative [tex]\( h'(4) \)[/tex] is:

[tex]\[ h'(4) = \frac{9}{8} \][/tex]

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