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

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M

manlymatt83

Lifer
Oct 14, 2005
10,051
44
91
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?
 
M

MrCodeDude

Lifer
Jun 23, 2001
13,674
1
76
The way you set up that problem, it would be:

int(13) dx

I'm pretty sure you meant: int(4x^2/(x^2 + 9))dx, yes?
 
Slimline

Slimline

Golden Member
Jul 19, 2004
1,365
2
81
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
 
H

hypn0tik

Diamond Member
Jul 5, 2005
5,866
2
0
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?
Click to expand...

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)
 
M

manlymatt83

Lifer
Oct 14, 2005
10,051
44
91
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?
Click to expand...

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)
Click to expand...


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....
 
H

hypn0tik

Diamond Member
Jul 5, 2005
5,866
2
0
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.
 
M

manlymatt83

Lifer
Oct 14, 2005
10,051
44
91
OK wait ...

You saw how many times x^2+9 went into 4x^2?

Sure ... x^2 goes into 4x^2 4 times, but what about the 9?
 
H

hypn0tik

Diamond Member
Jul 5, 2005
5,866
2
0
Originally posted by: mjuszczak
OK wait ...

You saw how many times x^2+9 went into 4x^2?

Sure ... x^2 goes into 4x^2 4 times, but what about the 9?
Click to expand...

Did you read my explanation?
 
M

manlymatt83

Lifer
Oct 14, 2005
10,051
44
91
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.
Click to expand...


Gotcha :) You're not in the NJ/PA/NY area are you? :)
 
H

hypn0tik

Diamond Member
Jul 5, 2005
5,866
2
0
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.
Click to expand...


Gotcha :) You're not in the NJ/PA/NY area are you? :)
Click to expand...

Nope. Sorry. I'm in Toronto.

This may help you out.
 
H

hypn0tik

Diamond Member
Jul 5, 2005
5,866
2
0
Originally posted by: mjuszczak
hypn0tik: BTW, what makes you so good at math? Do you use it daily?
Click to expand...

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?
Click to expand...
He's probably an engineer.
Click to expand...

Yep.
 
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