Find the approximated integral value of an equation 2x^3-4x+1 using Left endpoint approximation
a = 2 and b = 4
Step value (h) = 0.5

Solution:
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 Left endpoint approximation (Left Riemann Sum)


`int f(x) dx=Delta x xx(f(x_(0))+f(x_(1))+f(x_(2))+f(x_(3)))`

`=0.5xx(9+22.25+43+72.75)`

`=0.5xx(147)`

`=73.5`

Solution by Left endpoint approximation (Left Riemann Sum) is `73.5`

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