Find a root of an equation `f(x)=x^3+2x^2+x-1` using Fixed Point Iteration method
Solution:
Let `f(x) = x^3+2x^2+x-1`
Here `x^3+2x^2+x-1=0`
`:.x^3+2x^2+x=1`
`:.x(x^2+2x+1)=1`
`:.x=(1)/(x^2+2x+1)`
`:.phi(x)=(1)/(x^2+2x+1)`
Here
Here `f(0) = -1 < 0` and `f(1) = 3 > 0`
`:.` Root lies between `0` and `1`
`x_0 = (0 + 1)/2 = 0.5`
`x_1 = phi(x_0) = phi(0.5) = 0.44444`
`x_2 = phi(x_1) = phi(0.44444) = 0.47929`
`x_3 = phi(x_2) = phi(0.47929) = 0.45698`
`x_4 = phi(x_3) = phi(0.45698) = 0.47108`
`x_5 = phi(x_4) = phi(0.47108) = 0.46209`
`x_6 = phi(x_5) = phi(0.46209) = 0.46779`
`x_7 = phi(x_6) = phi(0.46779) = 0.46416`
`x_8 = phi(x_7) = phi(0.46416) = 0.46647`
`x_9 = phi(x_8) = phi(0.46647) = 0.465`
`x_10 = phi(x_9) = phi(0.465) = 0.46593`
`x_11 = phi(x_10) = phi(0.46593) = 0.46534`
`x_12 = phi(x_11) = phi(0.46534) = 0.46572`
Approximate root of the equation `x^3+2x^2+x-1` using Iteration method is `0.46572` (After 12 iterations)
`n` | `x_0` | `x_1=phi(x_0)` | Update | Difference `|x_1-x_0|` |
2 | 0.5 | 0.44444 | `x_0 = x_1` | 0.05556 |
3 | 0.44444 | 0.47929 | `x_0 = x_1` | 0.03485 |
4 | 0.47929 | 0.45698 | `x_0 = x_1` | 0.02231 |
5 | 0.45698 | 0.47108 | `x_0 = x_1` | 0.0141 |
6 | 0.47108 | 0.46209 | `x_0 = x_1` | 0.00899 |
7 | 0.46209 | 0.46779 | `x_0 = x_1` | 0.0057 |
8 | 0.46779 | 0.46416 | `x_0 = x_1` | 0.00363 |
9 | 0.46416 | 0.46647 | `x_0 = x_1` | 0.0023 |
10 | 0.46647 | 0.465 | `x_0 = x_1` | 0.00146 |
11 | 0.465 | 0.46593 | `x_0 = x_1` | 0.00093 |
12 | 0.46593 | 0.46534 | `x_0 = x_1` | 0.00059 |
13 | 0.46534 | 0.46572 | `x_0 = x_1` | 0.00038 |
This material is intended as a summary. Use your textbook for detail explanation.
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