derivitives

[gmontalv]

Will someone check my answers?

find the derivative.

f(x) = 4x^-3, find f(3)

My answer is f'(3) = -972


f(x) = 4 - 6 + 8
-- --- --- Find f(x)
x^1/2 x x^4

my answer is f'(x) = -2x^-3/2 + 6x^-2 - 32^-5



Find the slope of the line tangent to the graph of the function at the given value of x.
y= -8x^-1 + 5x^-2; x=2

My answer is y' = -48



Use product rule to find the derivative

f(x) = (3x-4) (x^1/2 +5)


My answer is 3/2x^1/2 - 2x^-1/2 +3/2x + 15


Use quotient rule to find derivative

y= x^2 + 8x + 3
-----------------
x^1/2


My answer 2x^7/2 + 12x^1/2 - 1/2x^3/2 + 3/2x^-1/2


Thanks

 

[Gene]

You lost a sign.
f(x) = 4x^-3, find f(3)
My answer is f'(3) = -972

f'(x) = (-3)*4*x^-4 = -12/x^4

It works better if you click twice on the C button then type between the

 boxes.
[code]
         4      6     8 
f(x) = ----- - --- + --- Find f(x) 
       x^1/2    x    x^4

[/code]
my answer is f'(x) = -2x^-3/2 + 6x^-2 - 32^-5
Good

My answer is y' = -48
Same mistake as in the first.

    x^2 + 8x + 3 
y= ----------------- 
      x^1/2

Better show your work. It's wrong but I can't guess why.
If x=1 y = 12,
if x=2 y = about 16 so
the slope is about 4 at x=1. Your answer gives about 15.