Question

The integral f(x) = 3x/5 -2 from 0 to 5 should give the answer 3. I get -2,5

My attempt:

F(x) = 3x² / 10 - 2x
F(x) = 3*5² / 10 - (2 * 5) = -2,5

Answer 1

As you can see, along our interval, e^(x) > e^(-3x), so our integral will be:

(e^(x) - e^(-3x)) * dx, from x = 0 to x = ln(5)

The integral of e^(x) * dx is e^(x)
The integral of e^(-3x) * dx is (-1/3) * e^(-3x)

e^(x) - (-1/3) * e^(-3x) + C =>
e^(x) + (1/3) * e^(-3x) + C

From 0 to ln(5)

e^(ln(5)) - e^(0) + (1/3) * e^(-3 * ln(5)) - (1/3) * e^(-3 * 0) =>
5 - 1 + (1/3) * 5^(-3) - (1/3) =>
4 - 1/3 + (1/3) * (1/125) =>
11/3 + 1/375 =>
(11 * 125 + 1) / 375 =>
(1375 + 1) / 375 =>
1376/375 =>
3.6693333333333333333333333333333

Answer 2

is that goood

Answer 3

integrate 3x/5 -2 ; [0,5]

since this is a poly, the 0 is pointless to us; this IS a poly right?

3(5)^2/10 - 2(5)

3(25)/10 - 10

75/10 - 10 = 7.5 - 10 = -2.5

Answer 4

0 to 5, or 0 to ln(5)?

Answer 5

hmm, I must be missing something; the answer should be 3... :/

Answer 6

0 to 5

Answer 7

I don't know what you mean by a poly

Answer 8

of the form\[c_0+c_1x+c_2x^2+...+c_nx^n\]
as opposed to a rational expression of some sort

Answer 9

poly is short for polynomial

Answer 10

hmm, no this is a straight line, so y = kx + m

Answer 11

a poly of degree 1 is a straight line

Answer 12

can you scan the problem? maybe your misreading something?

Answer 13

....or you might be looking at the wrong answer key, or the answer key may even have a wrong solution. That happens from time to time

Answer 14

I'm thinking the answer key seems to be wrong. There isn't much to misread and you seem to reach the same answer as me. So, I'm going to assume the answer 3 is wrong.

Help appreciated. :)

Answer 15

http://www.wolframalpha.com/input/?i=integrate+3x%2F5-2+dx%2C+from+0..5

just as a dbl chk :) good luck

Answer 16

thx