Posted by **Caroline** on Wednesday, October 26, 2011 at 9:41pm.

Find the total mass of the triangular region with coordinates (-1,0),(0,4),and (1,0). All lengths are in centimeters, and the density of the region is (x)=5+x grams/c^m2.

I know that to get the total mass i have to do density* lenght and ingegrate, but I dont know how to to it for a triangle...

- Calculus -
**bobpursley**, Wednesday, October 26, 2011 at 9:56pm
draw the triangle.

Notice the base is horizontal frm -1,0 to 1,0

write the equation for the two legs

left leg: y=mx+b where m= (4/1)=4

y=4x+b

4=4*0+b or b=4

integrating the left side..

mass=INT y*(5+x)dx fro x=-1 to 0 do that inegral. Now on the right side, the leg equation is y=-4x+4

same equation as above, integrate from x=0 to 1

be certain in each area to use as y either (-4x+4) or y=(4x+4)

add the two masses

- Calculus -
**Caroline**, Wednesday, October 26, 2011 at 10:38pm
What I did was:

INT (-1,0) (4x+4)(5+x) dx

INT 4x^+36x+20

I integrated and got (4/3)x^3+18x^2+20x

and evaluated from -1 to 0 and got 10/3 g and then from 0 to 1 and got 118/3 grams added and got 128/3 g and that's not the answer. What am I doing wrong?

- Calculus -
**Steve**, Thursday, October 27, 2011 at 12:22am
(4x+4)(5+x) = 4x^2 + 24x + 20

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