Kreshnik
\[\LARGE f'(x)=x^2+3x \;\; ,\;\; f(1)=5\;\;\;\;\Longrightarrow f(2)=?\]
I need some hints



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SUROJ
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f(x) can be obtained by integration........then use f(1) to find value of c, then find f(2)

Rohangrr
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ya suroj ur correctt

SUROJ
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got it?

Kreshnik
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\[\LARGE f(x)=\frac13 x^3 +\frac32 x^2 \;\;\;\;??\]

SUROJ
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you left +C at the end

SUROJ
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you need to add +C at end because it is integration

SUROJ
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indefinite integration

Kreshnik
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ok but... I need to firnd f(2) then how??

SUROJ
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on the second condition when x=1, y=5, you see , put those values and get c

Kreshnik
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\[\LARGE \int\limits x^2+3x \;dx = \frac13 x^3+\frac32x^2+C\]

SUROJ
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put the c back on f(x) and get complete f(x) equation and then find f(2)

SUROJ
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yes

Rohangrr
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correct

Kreshnik
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how can I know what the value of C is ??

Kreshnik
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I see it you told me before... let me try, I'll see what I can do :D

SUROJ
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see second condition f(1) is 5 than mean when x=1 , y=5

SUROJ
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see f(x) is what you get by integration

SUROJ
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because you integrate f'(x)

SUROJ
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did you catch it?

Kreshnik
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is C=19/6 ??

Kreshnik
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I'm still dizzy ! O_O

SUROJ
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yes you got it

SUROJ
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now put that C back in f(x)

SUROJ
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got it?

Kreshnik
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ahh yeah... now I'll do it thank you very much ;)

SUROJ
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no problem lol

JoshDavoll
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\[f \left( x \right) = x ^{2} + 3x\]
\[f \left( 1 \right) = 1^{2} + 3 \times 1 = 5\]
\[f \left( 2 \right) = 2^{2} + 3 \times 2 = 10\]
simple.

JoshDavoll
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@kreshnik another simple way to do something.

Kreshnik
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@JoshDavoll WRONG... the answer IS \[\frac{71}{6}\] !! Thanks for the help !

Kreshnik
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hahaha... obviously , you mus be 1012 years ... LOL