Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
malexander
Group Title
Hi. I wanted to know how does one know when to use the substitution rule for integrals and when not too?
 2 years ago
 2 years ago
malexander Group Title
Hi. I wanted to know how does one know when to use the substitution rule for integrals and when not too?
 2 years ago
 2 years ago

This Question is Closed

saifoo.khan Group TitleBest ResponseYou've already chosen the best response.0
@satellite73
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
take the derivative of u....if that du is present in the integrand you can use sub
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.1
don't use them on saturday night. go out and party
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
wait...we're talking about usub right? not algebraic sub?
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
lol sat
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
@lgbasallote yep I am. I wanted to know when you look at an integral problem, how do you know to use either usubstitution or not.
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
go out and integrate?
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
@malexander it involves mastery of derivatives...if you know many derivativves you can see them immediately...if not..you can try uing then derive it...
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.1
a function multiplied by something that is either the derivative, or a constant multiple of the derivative
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.1
\[\int\sqrt{x^3+3}x^2dx\] for example, because the derivative of \(x^3+3\) is \(3x^2\) and what i wrote above was wrong
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.1
should have been \[\int f(g(x))g'(x)dx\]
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
^integral of the chain rule
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
just noticed lo
 2 years ago

marcoduuuh Group TitleBest ResponseYou've already chosen the best response.0
Don't use it on Sundays either, yolo.
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
Your confusing me @satellite73. Um. Lets say you have these four integrals (question 2). In this question, which one would you need usubstitution and why?
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
Why those @lgbasallote ?
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
\[\large \int \frac{3x^3}{\sqrt{x^4 + 1}} = 3\int \frac{x^3}{\sqrt{x^4 + 1}}\] if i let u = x^4 + 1 du = 4x^3 the constant 4 is not important...but x^3 is...and it is present in the integrand so you can use usub
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
2d is usubbable too
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
Oh okay. That makes a bit more sense @lgbasallote . However, I thought we were not able to integrate fractions? (Im a cal 1 student, maybe inter grating fractions is in cal 2)
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
integrating fractions....for example 1/u^2 1/u^2 = u^(2) according to basic algebra according to basic integration...you can use power rule on that..i assume you're familiar with that note: NEVER use power rule on 1/u <the integral of that is automatically ln u
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
also note that i am using u...this is because u is a function of x meaning it is an expression..not limited to only a variable
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
right, i remember that @lgbasallote about 1/u^2..and also thats fine, we use "u" in class
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
@lgbasallote ln is in calc 2, so i hope i get to do that next semester hehe...i think i just need to do more problems with integration then...
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
i see...so you're just learning usub...try integrating the ones i said..2b and 2d
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
will do!
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
thanks again @lgbasallote ....i have another question...do u mind me asking it here, or posting another question box?
 2 years ago

lgbasallote Group TitleBest ResponseYou've already chosen the best response.1
new post...im too lagged for a long thread lol
 2 years ago

malexander Group TitleBest ResponseYou've already chosen the best response.0
LOL! ok sounds good
 2 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.