The Student Room Group

Help with Intergration

Hi.



Could someone explain how I can find k?
I expanded out the bracket and... do I intergrate by parts ? :s-smilie:

Thanks.
Reply 1
Original post by ℓove
Hi.



Could someone explain how I can find k?
I expanded out the bracket and... do I intergrate by parts ? :s-smilie:

Thanks.

Since k is a constant, you have something of the form

aebx+cedxae^{bx} + ce^{dx}

Does that help? You don't need integration by parts - it's much simpler than that.
Reply 2
I still don't understand -I'll just ask my teacher tomorrow.

Thank you anyway.
Reply 3
Original post by ℓove
I still don't understand -I'll just ask my teacher tomorrow.

Thank you anyway.

Okay but if you still want to have a go today:

If you had e2xe^{2x} then that integrates to give 12e2x(+c)\frac{1}{2}e^{2x} (+c)

So if you have (4k1)e2.5x(4k-1)e^{2.5x} then that integrates to give 12.5×(4k1)e2.5x\frac{1}{2.5}\times (4k-1)e^{2.5x}

And the second term can be integrated in a similar way.
Reply 4
Okay it's coming back to me now. :smile:

So I got k=4.36 rounded to 3 s.f. but the answer says k=4 ...would you know if I went wrong somewhere?

IMG_1883.jpg
Original post by ℓove
Okay it's coming back to me now. :smile:

So I got k=4.36 rounded to 3 s.f. but the answer says k=4 ...would you know if I went wrong somewhere?

IMG_1883.jpg


You have subtracted a negative value, so you need to add 2/5 and 2k.
Reply 6
Ooohh right!! :smile:)))) I understand now. Thank you both!
(edited 6 years ago)
Reply 7
Original post by r3035
....................so not a racist thread about migrants integrating into society ?


Hahahahah good one lol

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