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Derivative of Log base 4 [( x^2+1)]=y the long way?

Derivative of Log base 4 [( x^2+1)]=y the long way? Calc BC

if you change to 4^y=x^2+1 and then hy cant you NOT have the capatilized part? yln(4)=LN(X^2)+LN(1) ...why is that step not correct?

1 Answer

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  • Jeremy
    Lv 5
    7 years ago

    the logarithm function does not distribute over the addition like that,

    log(a + b)

    does not equal

    log(a) + log(b)

    we have:

    4^y = x^2 + 1

    ln(4^y) = ln(x^2 + 1)

    y*ln(4) = ln(x^2 + 1)

    ln(4) dy = 2x/(x^2 + 1) dx

    dy/dx = 2x/(x^2 + 1) * (1/ln(4))

    dy/dx = 2x/(x^2 + 1) * (1/ln(2^2))

    dy/dx = 2x/(x^2 + 1) * (1/(2ln(2)))

    dy/dx = x/(x^2 + 1) * (1/ln(2))

    dy/dx = x/[ln(2)*(x^2 + 1)]

    or, if u prefer:

    dy/dx = x/ln(2^(x^2 + 1))

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