Posted by **REALLY NEED HELP!!!!** on Friday, November 12, 2010 at 7:02pm.

Estimate the area under the graph of f(x)=x^2+2x from x = 4 to x = 10 using 3 approximating rectangles and left endpoints.

I got 290.25 as my answer but it's wrong. Would someone explain to me how to answer this question.

- Math: Calculus -
**bobpursley**, Friday, November 12, 2010 at 8:03pm
what is f(x) at x=4,6, 8

area=f(4)*2+f(6)*2 + f(8)*2

that is three rectangles of width 2, height to f(x)(left end point).

How in the world would you estimate to five digits of precision. "estimate"

f(4)=24

f(6)=48

f(8)=80

estimate: you do it. Twice the sum of those numbers.

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