Econ 302: Practice Questions 1


The following questions are a calculus review. If you master them then the level of calculus used in the class should not be a problem for you.

If you feel you need more practice, check the the following questions. If you just need a little bit of help click here for a short calculus review.





Question 1: Compute the first derivative of the following functions
  • f(x)=x2/(1+4x)
  • f(x)=ln(x+20) (recall that the derivative of ln(x) is 1/x).
  • f(x)=ln(x+a) where a is a fixed number.
    Note that if you choose a=20 the answer of both this question and the previous one must be the same.
  • f(x)=(4+x4)1/2
    Note that (...)1/2 is the same as the square root of (...).
  • f(x)=(a+x4)1/2 where a is a fixed number.
    Choose a=4 to check your answer.
  • f(x)=3x2+6x4.
  • f(x)=ax2+bx4 where a and b are fixed numbers.
    Choose a=3 and b=6 to check your answer.

Question 2: Compute the partial derivatives with respect to x and y for the functions listed below.

Note that if you take a partial derivative of a function with respect to one variable then you treat all other variable as if they were fixed numbers (i.e., in the questions above with numbers a or b you have essentially already taken a partial derivative).

  • f(x,y)=xy3
  • f(x,y)=x+20y
  • f(x,y)=10ln(x)+ln(y).
  • f(x,y)=(x+2y)/y.
  • f(x,y)=2x2+y.
  • f(x,y)=ax2+by where a and b are fixed numbers.
    Again, check your answer for a=2 and b=1

Question 3: The following exercises will be useful for graphing indifference curves.


  • Assume that x2y=20.
    • Write y as a function of x.
    • Graph the function for x>=0, where x is graphed on the horizontal axis, and y on the vertical axis.
    • Determine the slope at x=2.
    • Determine the value of y at x=2.
  • Now assume that the function is given by xy2=36.
    • Again write y as a function of x.
    • Graph the function for x>=0, where x is graphed on the horizontal axis, and y on the vertical axis.
    • Determine the slope at x=4.
    • Determine the value of y at x=4.

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