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find derivative of y=(x^2+1)(x^3+1) by using Product Rule?

I did d/dx(f(x)(g)(x)= f(x)d/dx [g(x)]+g(x)d/dx[f(x)] somehow I cannot get the answer to be y'=5x^4+3x^2+2x

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  • 1 decade ago
    Favorite Answer

    ... d(ab) = a d(b) + b d(a)

    f(x) = (x^2+1) (x^3+1)

    d[ f(x) ] = (x^2+1) d [ (x^3+1) ] + (x^3+1) d [ (x^2+1) ]

    .......... = (x^2+1) [3x^2] d [x] + (x^3+1) [2x] d [x]

    df/dx = (x^2+1) [3x^2] + (x^3+1) [2x]

    ....... = 3x^4 + 3x^2 + 2x^4 + 2x

    ....... = 5x^4 + 3x^2 + 2x

  • 1 decade ago

    to get that answer what you need to do is first

    (x^2+1)*dx(x^3+1)+(x^3+1)*dx(x^2+1)

    (x^2+1)*3x^2+(x^3+1)*2x

    so it will be

    3x^4+3x^2+2x^4+2x

    add the like terms

    5x^4+3x^2+2x

    and if you want you can factor one x to make it a bit more simple

  • 1 decade ago

    First, find your derivatives.

    In operator notation:

    Dx [x^2 + 1 ] = 2x.

    Dx [x^3 + 1 ] = 3x^2.

    Now we have f.Dx[g] + g.Dx[f] =

    (3x^2)(x^2 + 1) + (x^3 + 1)(2x).

    = 3x^4 + 3x^2 + 2x^4 + 2x.

    = 5x^4 + 3x^2 + 2x.

  • 1 decade ago

    y' = (x² + 1)(3x²) + (x³ + 1)(2x)

    y' = 3x^4 + 3x² + 2x^4 + 2x

    y' = 5x^4 + 3x² + 2x

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  • 4 years ago

    Use product rule. there is likewise some chain rule in looking the by-manufactured from (6-4x)^12 it is going to be the 1st circumstances the by-manufactured from the 2nd plus the 2nd circumstances the by-manufactured from the 1st: (x^8)*(a million/2)(6-4x)^(-a million/2)*(-4)+(6-4x)^a million... *(8x^7) i don't understand your alternatives although...

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