We'll apply Leibniz-Newton formula to evaluate the definite
integral:
Int f(x)dx = F(b) - F(a), where a and b are the limits of
integration.
First, we'll determine the indefinite integral. We'll
change the variable as method of solving the integral.
Int
x^2dx/sqrt(x^3 + 1)
We notice that if we'll put x^3 + 1 = t and
we'll differentiate, we'll get the numerator.
3x^2dx =
dt
x^2dx = dt/3
We'll re-write the
integral:
Int x^2dx/sqrt(x^3 + 1) = Int (dt/3)/sqrt
t
Int (dt/3)/sqrt t = (1/3)*Int dt/sqrt
t
(1/3)*Int dt/sqrt t = (1/3)*[t^(-1/2 + 1)/(-1/2 + 1)] +
C
(1/3)*Int dt/sqrt t = (2/3)*sqrt t +
C
Int f(x)dx = (2/3)*sqrt (x^3 + 1) +
C
We'll evaluate the definite integral, having as limits of
integration x = 2 and x = 3:
Int f(x)dx = (2/3)*sqrt (3^3 + 1) -
(2/3)*sqrt (2^3 + 1)
Int f(x)dx = (2/3)*(sqrt28 -
3)
Int f(x)dx = (2*sqrt28)/3 -
2
The definite integral of the function f(x) =
x^2/sqrt(x^3 + 1), is Int f(x)dx = (2*sqrt28)/3 - 2.
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