Q. - Let f be a function such that f(−2)=8 and f′(−2)=4.- Let h be the function h(x)=x3.Evaluate dxd[h(x)f(x)] at x=−2.
Given functions and rule: We are given the function f(x) and its derivative at x=−2, as well as the function h(x). To find the derivative of the quotient h(x)f(x), we will use the quotient rule, which states that the derivative of a quotient is given by:dxd[h(x)f(x)]=(h(x))2h(x)f′(x)−f(x)h′(x)
Find derivative of h(x): First, we need to find the derivative of h(x), which is h′(x). Since h(x)=x3, we can use the power rule to find h′(x). The power rule states that the derivative of xn is n⋅xn−1.So, h′(x)=dxd[x3]=3⋅x2.
Evaluate h′(x) at x=−2: Now we need to evaluate h′(x) at x=−2. Plugging in −2 for x, we get:h′(−2)=3∗(−2)2=3∗4=12.
Evaluate h(x) at x=−2: Next, we need to evaluate h(x) at x=−2. Plugging in −2 for x in h(x)=x3, we get:h(−2)=(−2)3=−8.
Apply quotient rule: Now we have all the values we need to apply the quotient rule:f(−2)=8 (given)f′(−2)=4 (given)h(−2)=−8 (calculated)h′(−2)=12 (calculated)Using the quotient rule:(d/dx)[(f(x)/h(x))] at x=−2 = (h(−2)f′(−2)−f(−2)h′(−2))/(h(−2))2
Calculate f(−2), f′(−2), h(−2), h′(−2): Plugging in the values we have: (d/dx)[(f(x)/h(x))] at x=−2 = ((−8)⋅4−8⋅12)/(−8)2
Plug in values for quotient rule: Now we perform the calculations:(dxd)(h(x)f(x)) at x=−2 = 64−32−96
Perform calculations: Simplify the numerator: (dxd)[h(x)f(x)] at x=−2 = −64128
Simplify numerator: Finally, divide the numerator by the denominator: (dxd)[h(x)f(x)] at x=−2 = −2
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