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find derivative using limit definition?

I just posted this but I put in the wrong function so here it is again

f(x) = √(3x)

find f '(x) using the limit definition f '(x) = lim as h approaches 0 of [f(x+h) - f(x)]/h

1 Answer

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  • Sid
    Lv 6
    1 decade ago
    Favorite Answer

    using first principle of derivatives we get f'(x) as

    √(3(x+h)) - √(3x) / h

    multiply and divide by √(3(x+h)) + √(3x), we will get

    [ (√(3(x+h)) - √(3x) ) * ( √(3(x+h)) + √(3x) ) ] / [ h * (√(3(x+h)) + √(3x) ) ]

    = [3(x+h) - 3x] / [ h * (√(3(x+h)) + √(3x) ) ]

    = 3h/ [ h * (√(3(x+h)) + √(3x) ) ]

    h cancels out and we are left with

    3/ [ √(3(x+h)) + √(3x) ]

    put limit h->0 in the denominator above and you will get

    3 / 2√(3(x)

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