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Mathematics 22 Online
OpenStudy (mathmusician):

Integration

OpenStudy (mathmusician):

For a continuous function f(x), f(1)=11, and \[\int\limits_{1}^{5}f'(x)dx = 9\] determine f(5).

OpenStudy (mathmusician):

@freckles

OpenStudy (freckles):

do you know what \[\int\limits f'(x) dx=?\]

OpenStudy (mathmusician):

9

OpenStudy (mathmusician):

oh wait that is the indefinte integral

OpenStudy (freckles):

that isn't what i'm asking your question has definite integral in it while I asked about indefinite integral

OpenStudy (freckles):

ok you got it :p

OpenStudy (freckles):

I mean you figured out I was asking about a indefinite integral

OpenStudy (mathmusician):

F(x)

OpenStudy (freckles):

you do know the derivative of f(x) is f'(x)

OpenStudy (freckles):

so the integral of f'(x) is f(x)+C

OpenStudy (freckles):

\[\int\limits f'(x) dx=f(x)+C\]

OpenStudy (freckles):

in definite integrals we don't need the C since they get cancel out in the simplifcation of a definite integral

OpenStudy (freckles):

\[\int\limits_a^b f'(x) dx=f(x)|_a^b =f(b)-f(a)\]

OpenStudy (freckles):

can you show me your equation you have after evaluating your definite integral on your left hand side of your equation you wrote

OpenStudy (mathmusician):

The left-hand side like Reiman sums?

OpenStudy (freckles):

no no

OpenStudy (freckles):

you have an equation

OpenStudy (freckles):

for example a=b the right hand expression of the equation is b and left hand expression of the equation is a

OpenStudy (mathmusician):

Oh duh

OpenStudy (freckles):

your left hand side looks like this \[\int\limits_1^5 f'(x)\]

OpenStudy (freckles):

I'm asking you to evaluate the definite integral here

OpenStudy (mathmusician):

we dont have f'(x) though

OpenStudy (freckles):

here is a hint: \[\int\limits_1^5 f'(x) dx=f(x)|_1^5=....\]

OpenStudy (mathmusician):

9 right?

OpenStudy (freckles):

don't look at the right hand side yet

OpenStudy (freckles):

I'm trying to get you the write the left hand side as f(5)-f(1)

OpenStudy (mathmusician):

4

OpenStudy (freckles):

f(5)-f(1)=9 you are given f(1)=11 f(5)-11=9 solve for f(5)

OpenStudy (mathmusician):

oh yah now i remember this

OpenStudy (freckles):

you are going to add what to both sides to do this?

OpenStudy (mathmusician):

20

OpenStudy (freckles):

yes f(5)=11+9 f(5)=20

OpenStudy (freckles):

do you have any questions on this one (I'm going to leave you if you don't)

OpenStudy (mathmusician):

My computer hit a lag spike

OpenStudy (mathmusician):

okay im good thanks

OpenStudy (mathmusician):

enjoy your lunch

OpenStudy (freckles):

I think I seen @zepdrix on he is really good at math too

OpenStudy (freckles):

Peace

OpenStudy (mathmusician):

Yup im a fan

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