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# C1 Integration question help!!! Watch

1. How do i go along to answer this and finding C?? I end up getting the wrong answer for C! please show me how to work this out!!
Thanks
Question is in attachment!!

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2. You know that xrootx is x^3/2, yes?
3. integrate normally, then sub x=4, and make y=35, solve for C
4. difficult to see the power of 5x, what is it?

EDIT: you might as well type it out for us
5. (Original post by cpm1)
You know that xrootx is x^3/2, yes?
yes when i integrated i got the following properly i get the following: 10x^1/2 +2/5x^5/2 +C

But then i know you have to find C but how do i do it? Please help!!!

Thanks
6. (Original post by ilyking)
difficult to see the power of 5x, what is it?

EDIT: you might as well type it out for us
its 5x^-1/2 + x root x

How to find C. can u kindly show me step by step!

Thanks
7. (Original post by mujahid_e3)
yes when i integrated i got the following properly i get the following: 10x^1/2 +2/5x^5/2 +C

But then i know you have to find C but how do i do it? Please help!!!

Thanks
You are given in the question that when and you now have the equation for so substitute the and values in. is what you need to add to the side with 4 substituted in to get 35.

is the constant of integration meaning that it remains constant regardless of the values you put in. Once you have found it, you can find y for any value of x.
8. (Original post by dstevens)
You are given in the question that when and you now have the equation for so substitute the and values in. is what you need to add to the side with 4 substituted in to get 35.

is the constant of integration meaning that it remains constant regardless of the values you put in. Once you have found it, you can find y for any value of x.
so it would be:
35= 10 * 4^1/2 + 2/5 * 4 ^5/2 ?
this is 35= ????
Thanks
9. (Original post by mujahid_e3)
so it would be:
35= 10 * 4^1/2 + 2/5 * 4 ^5/2 ?
this is 35= ????
Thanks
10*4^1/2 is the same as 10*sqrt(4) which equals 20

4^5/2 is the same as sqrt(4^5) which is sqrt(1024) which equals 32

So you have 35=20+32+C and you can solve for C
10. can really read the dy/dx part, i think its 5x^1/2 + xrootx

if you integrate that you'll get 10x^1/2 + 2/5 x^5/2 + C

we're give than when x=4 y =35

substitue x=4 into that equation

so 20 + 12.8 + C = 35
therefore C = 2.2

is that right?

y = 10x^1/2 + 2/5 x^5/2 + 2.2
11. (Original post by sohail.s)
can really read the dy/dx part, i think its 5x^1/2 + xrootx

if you integrate that you'll get 10x^1/2 + 2/5 x^5/2 + C

we're give than when x=4 y =35

substitue x=4 into that equation

so 20 + 12.8 + C = 35
therefore C = 2.2

is that right?

y = 10x^1/2 + 2/5 x^5/2 + 2.2
Yes your right i checked... But how did you get the C? i am a bit stuck!!! Because i wasnt sure how to work it out! can u plz show me?

Thanks
12. (Original post by mujahid_e3)
Yes your right i checked... But how did you get the C? i am a bit stuck!!! Because i wasnt sure how to work it out! can u plz show me?

Thanks
C is the constant of integration
to find C substitute youe value of x (given) into the equation you just found by integration
make the equation equal to the value of y (given) and solve to find C

after integrating

y= 10x^1/2 + 2/5 x^5/2 + C
we are told that y=35 when x=4

put x=4 into the equation y= (10*2) + (2/5 * 32) + C

y=35 so 20 + 12.8 + C = 35

therefore C = 2.2

so y= 10x^1/2 ~ 2/5x^5/2 + 2.2

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