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Matt's Math Thread --- I HAVE to pass Calc II

How did they do this long division?

They went from:

The integral of: (4x^2/x^2+9)dx

to:

The integral of: (4- (36/x^2+9))dx

Any idears?
 
Damn, ever since the embrace of calculators, I have avoided math, and the old "long division". wtf do you need to use this stuff in the real world. Looks cofusing as shite
 
Originally posted by: mjuszczak
How did they do this long division?

They went from:

The integral of: (4x^2/x^2+9)dx

to:

The integral of: (4- (36/x^2+9))dx

Any idears?

You don't need long divison for that. Add and subtract 36 from the numerator.

(4x^2 + 36 -36)/(x^2 + 9) = (4x^2 + 36)/(x^2 + 9) -36/(x^2+9) = 4 -36/(x^2+9)
 
Originally posted by: hypn0tik
Originally posted by: mjuszczak
How did they do this long division?

They went from:

The integral of: (4x^2/x^2+9)dx

to:

The integral of: (4- (36/x^2+9))dx

Any idears?

You don't need long divison for that. Add and subtract 36 from the numerator.

(4x^2 + 36 -36)/(x^2 + 9) = (4x^2 + 36)/(x^2 + 9) -36/(x^2+9) = 4 -36/(x^2+9)


The book did it long division

I'm beginning to think I need to take a few days off of work and just sit in the math lab all day long to catch up....
 
Here

Just like regular division.

Edit: An explanation.

Look at the first term of the denominator. What do you need to multiply x^2 with to get 4x^2? Obviously, you need to multiply by 4. Now, multiply x^2 + 9 by 4 to get 4x^2 +36. Subtract the result from 4x^2 to obtain -36 as your remainder.
 
Originally posted by: hypn0tik
Here

Just like regular division.

Edit: An explanation.

Look at the first term of the denominator. What do you need to multiply x^2 with to get 4x^2? Obviously, you need to multiply by 4. Now, multiply x^2 + 9 by 4 to get 4x^2 +36. Subtract the result from 4x^2 to obtain -36 as your remainder.


Gotcha 🙂 You're not in the NJ/PA/NY area are you? 🙂
 
Originally posted by: mjuszczak
Originally posted by: hypn0tik
Here

Just like regular division.

Edit: An explanation.

Look at the first term of the denominator. What do you need to multiply x^2 with to get 4x^2? Obviously, you need to multiply by 4. Now, multiply x^2 + 9 by 4 to get 4x^2 +36. Subtract the result from 4x^2 to obtain -36 as your remainder.


Gotcha 🙂 You're not in the NJ/PA/NY area are you? 🙂

Nope. Sorry. I'm in Toronto.

This may help you out.
 
Originally posted by: mjuszczak
hypn0tik: BTW, what makes you so good at math? Do you use it daily?

Yeah, I use it every day.

What makes me good at it? I really don't know. Thing is, I'm not even that good compared to some of my friends and classmates.

Originally posted by: Howard
Originally posted by: mjuszczak
hypn0tik: BTW, what makes you so good at math? Do you use it daily?
He's probably an engineer.

Yep.
 
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