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Question
Math
Posted 4 months ago

Let P(x)=73(x4)+5(x4)22(x4)3+6(x4)4P(x)=7-3(x-4)+5(x-4)^{2}-2(x-4)^{3}+6(x-4)^{4} be the fourth-degree Taylor polynomial for the function ff about 4 . Assume ff has derivatives of all orders for all real numbers.
(a) Find f(4)f(4) and f(4)f^{\prime \prime}(4).
(b) Write the second-degree Taylor polynomial for ff^{\prime} about 4 and use it to approximate f(4.3)f^{\prime}(4.3).
(c) Write the fourth-degree Taylor polynomial for g(x)=4xf(t)dtg(x)=\int_{4}^{x} f(t) d t about 4 .
(d) Can f(3)f(3) be determined from the information given? Justify your answer.
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Answer from Sia
Posted 4 months ago
Solution by Steps
step 1
To find f(4)f(4), we evaluate the polynomial P(x)P(x) at x=4x = 4
step 2
P(4)=73(44)+5(44)22(44)3+6(44)4=7P(4) = 7 - 3(4-4) + 5(4-4)^2 - 2(4-4)^3 + 6(4-4)^4 = 7
step 3
Therefore, f(4)=7f(4) = 7
step 4
To find f(4)f''(4), we need to differentiate P(x)P(x) twice and evaluate at x=4x = 4
step 5
P(x)=73(x4)+5(x4)22(x4)3+6(x4)4P(x) = 7 - 3(x-4) + 5(x-4)^2 - 2(x-4)^3 + 6(x-4)^4
step 6
P(x)=3+10(x4)6(x4)2+24(x4)3P'(x) = -3 + 10(x-4) - 6(x-4)^2 + 24(x-4)^3
step 7
P(x)=1012(x4)+72(x4)2P''(x) = 10 - 12(x-4) + 72(x-4)^2
step 8
P(4)=1012(44)+72(44)2=10P''(4) = 10 - 12(4-4) + 72(4-4)^2 = 10
step 9
Therefore, f(4)=10f''(4) = 10
step 10
To write the second-degree Taylor polynomial for f(x)f'(x) about x=4x = 4, we use P(x)P'(x)
step 11
P(x)=3+10(x4)6(x4)2+24(x4)3P'(x) = -3 + 10(x-4) - 6(x-4)^2 + 24(x-4)^3
step 12
The second-degree Taylor polynomial for f(x)f'(x) is P(x)3+10(x4)6(x4)2P'(x) \approx -3 + 10(x-4) - 6(x-4)^2
step 13
To approximate f(4.3)f'(4.3), we evaluate the second-degree Taylor polynomial at x=4.3x = 4.3
step 14
P(4.3)3+10(4.34)6(4.34)2P'(4.3) \approx -3 + 10(4.3-4) - 6(4.3-4)^2
step 15
P(4.3)3+10(0.3)6(0.3)2P'(4.3) \approx -3 + 10(0.3) - 6(0.3)^2
step 16
P(4.3)3+30.54=0.54P'(4.3) \approx -3 + 3 - 0.54 = -0.54
step 17
Therefore, f(4.3)0.54f'(4.3) \approx -0.54
step 18
To write the fourth-degree Taylor polynomial for g(x)=4xf(t)dtg(x) = \int_{4}^{x} f(t) dt about x=4x = 4, we integrate P(x)P(x)
step 19
g(x)=4x(73(t4)+5(t4)22(t4)3+6(t4)4)dtg(x) = \int_{4}^{x} (7 - 3(t-4) + 5(t-4)^2 - 2(t-4)^3 + 6(t-4)^4) dt
step 20
g(x)=7(x4)32(x4)2+53(x4)312(x4)4+65(x4)5g(x) = 7(x-4) - \frac{3}{2}(x-4)^2 + \frac{5}{3}(x-4)^3 - \frac{1}{2}(x-4)^4 + \frac{6}{5}(x-4)^5
step 21
Therefore, the fourth-degree Taylor polynomial for g(x)g(x) is 7(x4)32(x4)2+53(x4)312(x4)4+65(x4)57(x-4) - \frac{3}{2}(x-4)^2 + \frac{5}{3}(x-4)^3 - \frac{1}{2}(x-4)^4 + \frac{6}{5}(x-4)^5
step 22
To determine if f(3)f(3) can be found from the given information, we note that P(x)P(x) is centered at x=4x = 4
step 23
Since P(x)P(x) is a Taylor polynomial centered at x=4x = 4, it does not provide information about f(x)f(x) at x=3x = 3
step 24
Therefore, f(3)f(3) cannot be determined from the given information
Answer
f(4)=7f(4) = 7, f(4)=10f''(4) = 10, f(4.3)0.54f'(4.3) \approx -0.54, fourth-degree Taylor polynomial for g(x)g(x) is 7(x4)32(x4)2+53(x4)312(x4)4+65(x4)57(x-4) - \frac{3}{2}(x-4)^2 + \frac{5}{3}(x-4)^3 - \frac{1}{2}(x-4)^4 + \frac{6}{5}(x-4)^5, and f(3)f(3) cannot be determined.
Key Concept
Taylor Polynomial Approximation
Explanation
Taylor polynomials provide approximations of functions around a specific point, but they do not give information about the function at points far from the center of the polynomial.

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