Posted by Hannah on Saturday, February 5, 2011 at 11:31am.
Find the derivative of f(x)= 2 sqrt x at x=4.
i thought that the derivative would be 2 x^1/2 but I guess this is wrong.

Math  helper, Saturday, February 5, 2011 at 1:09pm
dy/dx 2x^(1/2)
2 * 1/2 x^(1/2  2/2)
2/2 x^(1/2) = x^(1/2) = 1/(sqrt(x))

Math  dave, Saturday, February 5, 2011 at 1:17pm
You have two problems here.
1. need D:f(x) = 2sqrtx
2. subsitute x=4 into derivative
D: 2sqrtx :
a) multiply power times coefficient; 1/2 * 2 = 1
b)power  1 = 1/2 1 = 1/2
c. f'(x) = x^1/2 or 1/sqrtx
substitute 4 for x and you should be there
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