Originally Posted by

**Frostking** I am just starting to learn about integrals. We are using dummy variables to solve integrals from say 1 to 3. When we finish the range of the integral changes and I am at a loss as to how to determine the new values.

For example if I have Integral from 0 to 1 of x (2 + 3x^2) dx

it becomes integral from 2 to 5 of u^1/2 du times 1/6

PLease explain how the 0 to 1 becomes 2 to 5 and since u = 2 + 3x^2 what happened to the x in the integral that precedes the (2 + 3x^2) ^1/2?????

Either my book is missing some basic explanations or I am just slowwwwww!