Let's solve the problem step by step.
Part (a): Identify f(x) and x0
The function f(x) for linear approximation needs to satisfy the relationship:
33124≈f(x0)+f′(x0)(x−x0)
The choice of f(x) is f(x)=3x=x1/3.
The given x0 is 3125 because it's close to 3124 and its cube root is easy to compute (33125=15).
f(x)=x1/3,x0=3125
Part (b): Linear approximation of 33124
Using the formula for linear approximation:
f(x)≈f(x0)+f′(x0)(x−x0)
- Compute f(x0)=33125=15.
- Derivative: f′(x)=31x−2/3, so f′(x0)=31(3125)−2/3=3⋅1521=6751.
- Substitute x=3124:
f(3124)≈15+6751(3124−3125)=15−6751=15−0.00148=14.99852
Thus:
33124≈14.9985
Part (c): Choose g(x) for Newton's Method
Newton's Method approximates roots of functions. To approximate 33124, we define g(x) such that g(33124)=0.
The obvious choice is:
g(x)=x3−3124
Part (d): Choose x0 (initial guess for Newton's Method)
To find an integer x0 close to 33124, consider 33125=15. Thus:
x0=15
Part (e): Perform two iterations of Newton's Method
Newton's Method formula is:
xn+1=xn−g′(xn)g(xn)
For g(x)=x3−3124, we have g′(x)=3x2. Starting with x0=15:
First Iteration:
x1=x0−g′(x0)g(x0)=15−3⋅152153−3124
- Compute g(15)=153−3124=3375−3124=251.
- Compute g′(15)=3⋅152=3⋅225=675.
- Substitute:
x1=15−675251=15−0.3719=14.6281
Second Iteration:
x2=x1−g′(x1)g(x1)
- Compute g(14.6281)=(14.6281)3−3124:
14.62813≈3125.854sog(14.6281)=3125.854−3124=1.854
- Compute g′(14.6281)=3⋅(14.6281)2:
14.62812≈214.082,sog′(14.6281)=3⋅214.082=642.246
- Substitute:
x2=14.6281−642.2461.854=14.6281−0.00289=14.6252
Thus, after two iterations:
x1≈14.6281,x2≈14.6252
Final Answers:
(a) f(x)=x1/3,x0=3125
(b) 33124≈14.9985
(c) g(x)=x3−3124
(d) x0=15
(e) x1≈14.6281,x2≈14.6252
Would you like detailed steps for any part or further clarifications?
Related Questions:
- How does linear approximation differ from Newton's Method?
- Why is f(x)=x1/3 chosen in this problem?
- How is the derivative f′(x) calculated for x1/3?
- What happens if x0 is not close to the true root in Newton's Method?
- How can the accuracy of Newton's Method be increased?
Tip: Newton's Method converges faster when the initial guess is close to the actual root.