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returnAP Calc Help

# of Responses: 5

Posted 2 years ago by Juliet

I'm currently taking AP calc AB and with the AP test a month away, I'm struggling with the process of integration with u subsitution. Can anybody go over the process? 


I got a 5 on the AP Calc Test last year, so I will give you my best shot.

Posted 2 years ago by Charly123

I think the trick to U subsitution is to find what to subsitute for U. 

For example, if you are trying to integrate, (x+1)^2. This is a hard equation to intergrate. However, the intergral of x^2 is easy. 

So if we set u = x+1, 

then we will be dealing with a much easier problem instead. 

In the end, I think the trick is just to try to as many different things to subsitute in for U until you arrive at an easily integratable equation. 


Posted 2 years ago by Charly123

I think the trickest part is when your dealing with fractions.

Posted 2 years ago by garylewis

An easy trick is to just check if any part of the function you have to integrate is the derivative of another part. That might sound weird but I'll show you an example.

Take the integral of xsin(x2). Now this might seem like a pain to integrate but you can see that the derivative of x is 2x and we have an x in the equation.If we set u = x then du/dx = 2x if we manipulate this we can get du/2 = xdx. Now we can go back and plug in. The integral of xsin(x2)dx becomes the integral of (1/2)sin(u)du. This is a lot nicer to integrate giving us (-1/2)cos(u). Now you just plug u back in and get (-1/2)cos(x2), which is your answer. Hopefully my example helped and if you have anymore questions feel free to ask.



Posted 2 years ago by DabHaus

Once your get the hang of it, look through the Chapter 4 worksheets for it on the website. My teacher's website is a pretty good tool. If you find the worksheet, maybe you could print it out and ask your teacher to help you go through the problems you need. 

Posted 2 years ago by blipsandchitz