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can you integrate this....?

3x(4x-1)^1/2 using the method of changing variables! Give the answer in its simplest form

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  • Favourite answer

    very easy girl...

    see ,

    first use, 4x-1=t^2;

    then ,

    integration willl become-

    (3/4) * t (t^2 + 1);

    then open all the brackets and solve;

    i think now u can do it.

  • 1 decade ago

    3x( 4x - 1)^1/2

    let ( 4x - 1)^1/2 = t

    4x - 1 = t^2

    x = 1/4( t^2 + 1 ) . . . . . substitute

    3x( 4x - 1)^1/2 = 3/4 ( t^2 + 1 ) t^2

    integ 3/4 ( t^4 + t^2 ) dt = 3/4 ( t^5/5 + t^3/3 )

    . . . . = 3/4 [ (4x -1)^3/2 + 4x -1 ]

  • 1 decade ago

    fine..

    let 4x-1=t^2.

    it implies 4dx= 2tdt implies dx=t/2 *dt.

    now the integrand becomes 3*[t^2+1]/4 *t * t/2*dt

    now u can proceed ..........( just open the brackets and integration becomes easy.

    actually its a difficult job to write down each step.

    so a little hint may be sufficient for catching the problem.

  • 1 decade ago

    in(3x(4x-1)^1/2)dx

    Let u^2=4x-1

    2udu=4dx

    4x=u^2-1

    3/8*int( (u^2+1)*u*u) du

    =3/8 in(u^4+u^2 )du = 3/8*(u^5/5+u^3/u)+c

    where u=sqrt()4x-1)

  • 1 decade ago

    lets take 4x-1=t^2

    x= t^2/4+1/4

    dx= 2t/4=t/2

    now 3x(4x-1)^1/2 becomes 3(t^2/4+1/4)(t)(t/2)

    expanding 3/8t^4+3/8t^2

    integration gives you 3/40 (t^5) + 3/24 (t^3)

    ie 3/4(t^3)(t^2+1/6)

    ie 3/4(4x-1)^3/2(4x-5/6)

  • 1 decade ago

    are there limits? or is it purely S 3x(4x-1)^1/2 dx

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