Q. Let f(x)=x+23x2+1.Find f′(−3).Choose 1 answer:(A) 10(B) −10(C) −28(D) 28
Apply Quotient Rule: To find the derivative of the function f(x)=x+23x2+1, we will use the quotient rule. The quotient rule states that if we have a function that is the quotient of two functions, v(x)u(x), then its derivative is given by (v(x))2v(x)⋅u′(x)−u(x)⋅v′(x). Here, u(x)=3x2+1 and v(x)=x+2.
Find u′(x): First, we need to find the derivative of u(x)=3x2+1. The derivative of 3x2 is 6x, and the derivative of a constant is 0. Therefore, u′(x)=6x.
Find v′(x): Next, we need to find the derivative of v(x)=x+2. The derivative of x is 1, and the derivative of a constant is 0. Therefore, v′(x)=1.
Apply Quotient Rule: Now we apply the quotient rule. The derivative of f(x), denoted as f′(x), is given by:f′(x)=(x+2)2(x+2)⋅(6x)−(3x2+1)⋅(1).
Simplify f′(x): We simplify the expression for f′(x):f′(x)=(x+2)26x2+12x−3x2−1.
Combine Like Terms: Further simplifying, we combine like terms in the numerator: f′(x)=(x+2)23x2+12x−1.
Evaluate at x=−3: Now we need to evaluate f′(x) at x=−3. We substitute −3 into the derivative: f′(−3)=((−3)+2)23(−3)2+12(−3)−1.
Calculate Numerator and Denominator: We calculate the numerator and the denominator separately:Numerator: 3(−3)2+12(−3)−1=3(9)−36−1=27−36−1=−10.Denominator: ((−3)+2)2=(−1)2=1.
Divide Numerator by Denominator: Now we divide the numerator by the denominator: f′(−3)=(−10)/1=−10.
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