integration tutorial: analysis

Consider the integral
int 3e6p - 2e4p dp
This is an indefinite integral, so we need to find the most general antiderivative of the integrand f(p).
To find an antiderivative of f(p), we go through our list of integration methods:
  1. Recognize elementary antiderivatives
  2. Rewrite the integrand to make it easier
  3. Use substitution to reverse the chain rule or simplify the integrand
  4. Use integration by parts
  5. Use inspection to see the value of a definite integral
to find one that works for this integrand. In this case, only one method is appropriate. We can rewrite the integrand: consider the parts of the integral separately to give an expression that is more easily integrable. This is shown below.
Rewriting:
Consider the parts of the integral separately. This can be broken into separate integrals,
int 3e6p - 2e4p dp =int3e6pdp+int-2e4pdp
which can be evaluated using substitution (of "ax"), and substitution (of "ax"), respectively, to obtain
int3e6pdp+int-2e4pdp = ((1/2) e6p) + (-(1/2) e4p) + C.

Explanation for rewritten term(s)
Substitution (of "ax")
Let w = 6 p. Then w' = 6, so (1/6) dw = dp. The integral can therefore be rewritten as
int 3e6p dp = int 3ew (1/6) dw = (1/2) ew + C
Thus, substituting back for w,
int 3e6p dp = (1/2) e6p + C

Substitution (of "ax")
Let w = 4 p. Then w' = 4, so (1/4) dw = dp. The integral can therefore be rewritten as

int -2e4p dp = int -2ew (1/4) dw = -(1/2) ew + C
Thus, substituting back for w,
int -2e4p dp = -(1/2) e4p + C

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integration analysis
Last Modified: Wed Feb 6 13:53:59 EST 2002
Comments to glarose@umich.edu
©2002 Gavin LaRose, UM Math Dept.