Find the approximated integral value of an equation 2x^3-4x+1 using Simpson's 1/3 rule
a = 2 and b = 4
Step value (h) = 0.5Solution:Equation is `f(x)=2x^3-4x+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)=9` |
| `x_1=2.5` | `f(x_(1))=f(2.5)=22.25` |
| `x_2=3` | `f(x_(2))=f(3)=43` |
| `x_3=3.5` | `f(x_(3))=f(3.5)=72.75` |
| `x_4=4` | `f(x_(4))=f(4)=113` |
Method-1:Using Simpsons `1/3` Rule
`int f(x) dx=(Delta x )/3 (f(x_(0))+4(f(x_(1))+f(x_(3))+f(x_(5))+...+f(x_(n-1)))+2(f(x_(2))+f(x_(4))+f(x_(6))+...+f(x_(n-2)))+f(x_(n)))`
`int f(x) dx=(Delta x )/3 [f(x_(0))+4f(x_(1))+2f(x_(2))+4f(x_(3))+f(x_(4))]`
`f(x_(0))=9`
`4f(x_(1))=4*22.25=89`
`2f(x_(2))=2*43=86`
`4f(x_(3))=4*72.75=291`
`f(x_(4))=113`
`int f(x) dx=0.5/3*(9+89+86+291+113)`
`=0.5/3*(588)`
`=98`
Solution by Simpson's `1/3` Rule is `98`
Method-2:Using Simpsons `1/3` Rule
`int f(x) dx=(Delta x )/3 (f(x_(0))+4(f(x_(1))+f(x_(3))+f(x_(5))+...+f(x_(n-1)))+2(f(x_(2))+f(x_(4))+f(x_(6))+...+f(x_(n-2)))+f(x_(n)))`
`int f(x) dx=(Delta x )/3 [(f(x_(0))+f(x_(4)))+4(f(x_(1))+f(x_(3)))+2(f(x_(2)))]`
`=0.5/3 [(9 +113)+4xx(22.25+72.75)+2xx(43)]`
`=0.5/3 [(9 +113)+4xx(95)+2xx(43)]`
`=0.5/3 [(122)+(380)+(86)]`
`=98`
Solution by Simpson's `1/3` Rule is `98`
This material is intended as a summary. Use your textbook for detail explanation.
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