How do you use the limit definition to find the derivative of #f(x)=(2-x)/(3x+1)#?

Answer 1

#d/(dx) ((2-x)/(3x+1)) = -7/(3x+1)^2#

By definition the derivative of #f(x)# is:
#lim_(Deltax->0) (f(x+Deltax)-f(x))/(Deltax) = lim_(Deltax->0) (Deltaf)/(Deltax)#

Calculate:

#Deltaf = (2-(x+Deltax))/(3(x+Deltax)+1) - (2-x)/(3x+1)#
#Deltaf =( (2-x-Deltax)(3x+1) -(3x+3Deltax+1) (2-x))/((3x+3Deltax+1)(3x+1))#
#Deltaf =( cancel((2-x)(3x+1))-Deltax(3x+1) -cancel((3x+1) (2-x))-3Deltax(2-x))/((3x+3Deltax+1)(3x+1))#
#Deltaf = ( -Deltax(3x+1+6-3x))/((3x+3Deltax+1)(3x+1)) = -(7Deltax)/((3x+Deltax+1)(3x+1)) #
Divide by #Deltax#:
#(Deltaf)/(Deltax) = -7/((3x+Deltax+1)(3x+1)) #

Passing to the limit:

#lim_(Deltax->0) (Deltaf)/(Deltax) = lim_(Deltax->0) -7/((3x+Deltax+1)(3x+1)) = - 7/((3x+1)^2)#
Sign up to view the whole answer

By signing up, you agree to our Terms of Service and Privacy Policy

Sign up with email
Answer 2

To use the limit definition to find the derivative of the function (f(x) = \frac{2 - x}{3x + 1}), you first find the difference quotient (\frac{f(x + h) - f(x)}{h}), then take the limit as (h) approaches (0). This gives the derivative of the function (f(x)).

Sign up to view the whole answer

By signing up, you agree to our Terms of Service and Privacy Policy

Sign up with email
Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

Not the question you need?

Drag image here or click to upload

Or press Ctrl + V to paste
Answer Background
HIX Tutor
Solve ANY homework problem with a smart AI
  • 98% accuracy study help
  • Covers math, physics, chemistry, biology, and more
  • Step-by-step, in-depth guides
  • Readily available 24/7