Q. Given the function f(x)=(7−8x−10x3)(−6x2−5), find f′(x) in any form.Answer: f′(x)=
Product Rule Explanation: To find the derivative of the function f(x)=(7−8x−10x3)(−6x2−5), we will use the product rule. The product rule states that the derivative of a product of two functions is the derivative of the first function times the second function plus the first function times the derivative of the second function.
Define Functions: Let's denote the first function as u(x)=7−8x−10x3 and the second function as v(x)=−6x2−5. We will find the derivatives of u(x) and v(x) separately.
Derivative of u(x): The derivative of u(x)=7−8x−10x3 with respect to x is u′(x)=0−8−30x2. Simplifying, we get u′(x)=−8−30x2.
Derivative of v(x): The derivative of v(x)=−6x2−5 with respect to x is v′(x)=−12x−0. Simplifying, we get v′(x)=−12x.
Apply Product Rule: Now, we apply the product rule: f′(x)=u′(x)v(x)+u(x)v′(x). Substituting the derivatives we found, we get f′(x)=(−8−30x2)(−6x2−5)+(7−8x−10x3)(−12x).
Distribute Terms: We will now distribute the terms in the expression f′(x)=(−8−30x2)(−6x2−5)+(7−8x−10x3)(−12x). This involves multiplying each term in the first product and adding it to the result of multiplying each term in the second product.
First Product Simplification: Multiplying the terms in the first product, we get: (−8)(−6x2)+(−8)(−5)+(−30x2)(−6x2)+(−30x2)(−5). This simplifies to 48x2+40−180x4+150x2.
Second Product Simplification: Multiplying the terms in the second product, we get: (7)(−12x)+(−8x)(−12x)+(−10x3)(−12x). This simplifies to −84x+96x2+120x4.
Combine Results: Adding the results from the two products, we get f′(x)=(48x2+40−180x4+150x2)+(−84x+96x2+120x4).
Correct v′(x): Combining like terms, we get f′(x)=−180x4+120x4+48x2+150x2+96x2+40−84x. This simplifies to f′(x)=−60x4+294x2−84x+40.
Reapply Product Rule: Correcting the derivative of v(x), we have v′(x)=−12x. Now we will reapply the product rule with the correct derivatives: f′(x)=u′(x)v(x)+u(x)v′(x)=(−8−30x2)(−6x2−5)+(7−8x−10x3)(−12x).
First Product with Correct Derivative: Multiplying the terms in the first product with the correct derivative, we get: (−8)(−6x2)+(−8)(−5)+(−30x2)(−6x2)+(−30x2)(−5). This simplifies to 48x2+40+180x4−150x2.
Second Product with Correct Derivative: Multiplying the terms in the second product with the correct derivative, we get: (7)(−12x)+(−8x)(−12x)+(−10x3)(−12x). This simplifies to −84x+96x2+120x4.
Combine Results with Correct Derivatives: Adding the results from the two products with the correct derivatives, we get f′(x)=(48x2+40+180x4−150x2)+(−84x+96x2+120x4).
Combine Results with Correct Derivatives: Adding the results from the two products with the correct derivatives, we get f′(x)=(48x2+40+180x4−150x2)+(−84x+96x2+120x4). Combining like terms with the correct derivatives, we get f′(x)=180x4+120x4+48x2−150x2+96x2+40−84x. This simplifies to f′(x)=300x4−6x2−84x+40.
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