Need to verify the answer to an integrals question

[Howard]

Originally posted by: Heisenberg

Originally posted by: Howard
Somebody tell me if it's the integral of (y^2 - y - 2) from -1 to 2, please. If that isn't wrong, I don't see how I'm getting -31/6.

The integral of (y^2 - y - 2) from -1 to 2 is -9/2 according to my TI-89.

WTF

OK, I'm going to scan in my steps. One moment...

EDIT: Found my mistake... I calculated (-1)^3 = 1, for some reason.

 

[shelaby]

ya i got 9/2 too, TheLonelyPhoenix did it coreectly, dont know why you arent getting the correct answer

 

[Aves]

Originally posted by: Heisenberg
The integral of (y^2 - y - 2) from -1 to 2 is -9/2 according to my TI-89.

It should be the integral of (y + 2 - y^2) which is 9/2.

 

[Heisenberg]

Originally posted by: aves2k

Originally posted by: Heisenberg
The integral of (y^2 - y - 2) from -1 to 2 is -9/2 according to my TI-89.

It should be the integral of (y + 2 - y^2) which is 9/2.

It doesn't really matter. The negative sign just tells you which area was greater to begin with.

 

[Howard]

Figured out my mistake, thanks for the help, guys.

 

[Aves]

Originally posted by: Heisenberg

Originally posted by: aves2k

Originally posted by: Heisenberg
The integral of (y^2 - y - 2) from -1 to 2 is -9/2 according to my TI-89.

It should be the integral of (y + 2 - y^2) which is 9/2.

It doesn't really matter. The negative sign just tells you which area was greater to begin with.

I get you. I just figured that if he integrated it that way he would come up with 9/2 exactly without having to worry about changing the sign.

There's obviously not negative area.