There is no hard and fast rule for deciding what to set u equal to. Rather, it is one of those things one learns by experience. A useful -- although not 100% reliable -- rule of thumb is this: Put u equal to the expression that is being raised to an exponent or occurs in the exponent.

Here, the quantity 3x²+3 is being raised to a power, so we set u = 3x²+3.

Just close this window to return to the tutorial.
Lost the tutorial to which this window is attached? Press here.