What would you like to understand?

The bounds must be converted because the variable of integration changes from $u$ to $x$. The original bounds correspond to values of $u$, but the new integral is evaluated with respect to $x$.

Conditions: The integral is a definite integral.; A substitution $x = g(u)$ is performed.; The variable of integration changes from $u$ to $x$.

The bounds must be converted because the variable of integration changes from $u$ to $x$. The original bounds correspond to values of $u$, but the new integral is evaluated with respect to $x$.

Conditions: The integral is a definite integral.; A substitution $x = g(u)$ is performed.; The variable of integration changes from $u$ to $x$.