Find the approximated integral value of an equation x^3-2x+1 using Simpson's 3/8 rule
a = 2 and b = 4
Step value (h) = 0.5Solution:Equation is `f(x)=x^3-2x+1`
`a=2`
`b=4`
The value of table for `x` and `f(x)`
| `x` | `f(x)` |
| `x_0=2` | `f(x_(0))=f(2)=5` |
| `x_1=2.5` | `f(x_(1))=f(2.5)=11.625` |
| `x_2=3` | `f(x_(2))=f(3)=22` |
| `x_3=3.5` | `f(x_(3))=f(3.5)=36.875` |
| `x_4=4` | `f(x_(4))=f(4)=57` |
Method-1:Using Simpson's `3/8` Rule
`int f(x) dx=(3Delta x )/8 (f(x_(0))+2(f(x_(3))+f(x_(3))+...+f(x_(n-3)))+3(f(x_(1))+f(x_(2))+f(x_(4))+f(x_(5))+...+f(x_(2))+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(3Delta x )/8 [f(x_(0))+3f(x_(1))+3f(x_(2))+2f(x_(3))+f(x_(4))]`
`f(x_(0))=5`
`3f(x_(1))=3*11.625=34.875`
`3f(x_(2))=3*22=66`
`2f(x_(3))=2*36.875=73.75`
`f(x_(4))=57`
`int f(x) dx=(3xx0.5)/8 *(5+34.875+66+73.75+57)`
`=(3xx0.5)/8 *(236.625)`
`=44.3672`
Solution by Simpson's `3/8` Rule is `44.3672`
Method-2:Using Simpson's `3/8` Rule
`int f(x) dx=(3Delta x )/8 (f(x_(0))+2(f(x_(3))+f(x_(3))+...+f(x_(n-3)))+3(f(x_(1))+f(x_(2))+f(x_(4))+f(x_(5))+...+f(x_(2))+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(3Delta x )/8 [(f(x_(0))+f(x_(4)))+2(f(x_(3)))+3(f(x_(1))+f(x_(2)))]`
`=(3xx0.5)/8 [(5 +57)+2xx(36.875)+3xx(11.625+22)]`
`=(3xx0.5)/8 [(5 +57)+2xx(36.875)+3xx(33.625)]`
`=(3xx0.5)/8 [(62)+(73.75)+(100.875)]`
`=44.3672`
Solution by Simpson's `3/8` Rule is `44.3672`
This material is intended as a summary. Use your textbook for detail explanation.
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