What is the Purpose of U Substitution in Solving Integrals?

In summary, U substitution is a technique used in integration to simplify complex integrals by replacing a variable with a new variable, u. It is most commonly used for integrals involving a composite function and the appropriate u should be chosen to simplify the integrand. However, U substitution is not applicable to all integrals and may not always lead to a simpler integral, so it is important to understand its limitations and when to use it effectively.
  • #1
bmed90
99
0

Homework Statement




the integral of 1/(1-y)dy

Homework Equations





The Attempt at a Solution



ln|1-y|+C

however I believe you use u substitution as 1-y=U? Why is this so?


 
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  • #2
You lost a minus sign in your solution. Making a substitution would work because the integral would reduce to
[tex]\int{-\frac{1}{u}du}[/tex]
which is well known, but this example is simple enough that you could solve it just by looking at it.
 

FAQ: What is the Purpose of U Substitution in Solving Integrals?

Why do we use U substitution in integration?

U substitution is a technique used in integration to simplify complex integrals. It involves replacing a variable in the integral with a new variable, u, to make the integral easier to solve. This allows us to use the basic integration rules and formulas to solve the integral.

When should we use U substitution in integration?

U substitution is most commonly used when the integrand contains a composite function, such as f(g(x)), where g(x) is an inner function. In these cases, we can use U substitution to replace the inner function with a new variable, making the integral easier to solve.

How do we choose the appropriate u for U substitution?

The key to choosing the appropriate u for U substitution is to look for a function within the integral that resembles one of the basic integration formulas. The variable u should be chosen so that when substituted into the integral, it simplifies the integrand and makes it easier to solve.

Can U substitution be used for all integrals?

No, U substitution is not applicable to all integrals. It is most commonly used for integrals involving a composite function, but may not work for other types of integrals. Other techniques, such as integration by parts or trigonometric substitution, may be more appropriate for these cases.

Are there any limitations to using U substitution in integration?

Yes, there are some limitations to using U substitution. It may not work for all integrals and may not always lead to a simpler integral. In some cases, it may even make the integral more complicated. It is important to practice and develop an understanding of when and how to use U substitution effectively.

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