silemus.

13Chain rule on square root

Let f(x)=3x+1\displaystyle f(x) = \sqrt{3x + 1}. Find f′(1)\displaystyle f'(1).

Rewrite √(3x+1) as (3x+1)^(1/2) and use the chain rule: f'(x) = 3/(2√(3x+1)). At x=1, that's 3/(2√4) = 3/4.

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