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Find [tex]\(\frac{d y}{d x}\)[/tex] when

(i) [tex]\(y=\left(x^2 + 2x - 1\right)^5\)[/tex]


Sagot :

To find the derivative [tex]\(\frac{dy}{dx}\)[/tex] of the function [tex]\( y = \left(x^2 + 2x - 1\right)^5 \)[/tex], we will use the chain rule. The chain rule allows us to differentiate composite functions.

Here is a detailed step-by-step solution:

1. Identify the outer and inner functions:

The function can be thought of as a composition of two functions. Let
[tex]\[ u = x^2 + 2x - 1 \][/tex]
and hence,
[tex]\[ y = u^5 \][/tex]

2. Differentiate the outer function with respect to [tex]\(u\)[/tex]:

The outer function is [tex]\(y = u^5\)[/tex]. Using the power rule, the derivative of [tex]\(y\)[/tex] with respect to [tex]\(u\)[/tex] is:
[tex]\[ \frac{d y}{d u} = 5u^4 \][/tex]

3. Differentiate the inner function with respect to [tex]\(x\)[/tex]:

The inner function is [tex]\(u = x^2 + 2x - 1\)[/tex]. Differentiating [tex]\(u\)[/tex] with respect to [tex]\(x\)[/tex] gives:
[tex]\[ \frac{d u}{d x} = 2x + 2 \][/tex]

4. Apply the chain rule:

The chain rule states that:
[tex]\[ \frac{d y}{d x} = \frac{d y}{d u} \cdot \frac{d u}{d x} \][/tex]
Substituting in the derivatives found in steps 2 and 3:
[tex]\[ \frac{d y}{d x} = 5u^4 \cdot (2x + 2) \][/tex]

5. Substitute back [tex]\(u = x^2 + 2x - 1\)[/tex]:

Replace [tex]\(u\)[/tex] with the original expression [tex]\(x^2 + 2x - 1\)[/tex]:
[tex]\[ \frac{d y}{d x} = 5(x^2 + 2x - 1)^4 \cdot (2x + 2) \][/tex]

6. Simplify the expression:

Factor out common terms in the derivative expression:
[tex]\[ \frac{d y}{d x} = (10x + 10)(x^2 + 2x - 1)^4 \][/tex]

Thus, the derivative of [tex]\( y = \left(x^2 + 2x - 1\right)^5 \)[/tex] with respect to [tex]\(x\)[/tex] is:
[tex]\[ \frac{dy}{dx} = (10x + 10)(x^2 + 2x - 1)^4 \][/tex]