these, whenever u is a function of x, we define du to be u ′(x) dx; when u is a function of t, we define
du to be u ′(t) dt; and so on.
EXAMPLE 1EXAMPLE 2
EXAMPLE 3
EXAMPLE 4
is integrated most efficiently by using formula (3) with u = 1 − 3x and du = u ′(x)dx =
−3 dx.