# Definite integral problem

• Nov 20th 2009, 04:10 AM
CleanSanchez
Definite integral problem
So I have the integral $\int - \frac{3y^2}{2}$ over 0 to 4.

Every computer software evaluates this as -32 which is the correct answer but I keep getting -24... what am I doing wrong? Any help is appreciated!
• Nov 20th 2009, 04:19 AM
Defunkt
Show some work so we can tell you where you went wrong and what you need to do :)
• Nov 20th 2009, 04:30 AM
CleanSanchez
Original integral $\int - \frac{3y^2}{2}$ over 0 to 4.

Well I did $-\frac {(3)(4^2)}{2} = -\frac {(3)(16)}{2} = -\frac {48}{2} = -24$

and 0 makes the whole second fraction 0 so we can ignore it... but apparently I'm wrong (Crying)
• Nov 20th 2009, 04:34 AM
Defunkt
Quote:

Originally Posted by CleanSanchez
Original integral $\int - \frac{3y^2}{2}$ over 0 to 4.

Well I did $-\frac {(3)(4^2)}{2} = -\frac {(3)(16)}{2} = -\frac {48}{2} = -24$

and 0 makes the whole second fraction 0 so we can ignore it... but apparently I'm wrong (Crying)

Did you not forget to integrate? :P
• Nov 20th 2009, 04:42 AM
CleanSanchez
Ah yes, I was getting ahead of myself and thats not where my mistake was. It's part of a larger double integral problem and the bounds of x are 0 - 2 not 0 -4. Reversing double integrals can get confusing!