For solving the integral, we'll apply integration by
parts:
Int f(x)dx = Int x*ln
xdx
We'll apply the formula of integration by
parts:
Int udv = uv - Int
vdu
u = ln x
We'll
differentiate both sides:
du =
dx/x
dv = xdx => Int xdx = Int dv =
v
v = x^2/2
We'll substitute
u,v,du,dv in the formula above:
Int x*ln xdx = [(x^2)*(ln
x)]/2 - Int x^2dx/2x
We'll simplify and we'll
get:
Int x*ln xdx = [(x^2)*(ln x)]/2 - x^2/4 +
C
We'll factorize by
x^2/2:
Int x*ln xdx = (x^2/2)*(ln x - 1/2) +
C
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