integral from -2 to -8

(10x–9x^2)dx

use midpoint approximation with n=3

my points were
(-8,-6)
(-6,-4)
(-4,-2)

i added them up and dividded by two the plugged it into the orginal eqautipon.

The number i got i added and multpiled by three but still got the wrong answer.

Please help me!

If I understand correctly what you mean by

"midpoint approximation" you are splitting the region up into 3 rectangles, each has a width of 2
and its height is determined by the midpoint of the base of each of the rectangles.

first of all I don't see where your points come from.

the left-most rectangle goes from -8 to -6, so its base runs along (-7,-511)
(sub -7 into your given function to get -511)
similarly the middle rectangle has its base on (-5,-275) and the righ-most rectangle has its base on (-3,-111)

the the area would be
2x511 + 2x275 + 2x111 = 1794

(The accurate Calculus calculation gave me 1812, so not bad for the above result)