Tuesday, January 18, 2011

Functions

Hi
     It's kiran
  Today short peiod because if T.A. so today we did one to one function.                                                  
    Definition
    Function is defined as a relation of x,y where for every x there is one and only one value of y assigend . A one to one funtion has another restriction added on to this : For every y which hass been assigned to the x's no other x has that y (for every y there is one and only one value x)

Examples -:
Question 1: Is function f defined by


f = {(1 , 2),(3 , 4),(5 , 6),(8 , 6),(10 , -1)}
,

a one to one function?
Solution to Question 1:
  . Two different valuse in the damain namely %and 6 have same output, hence function f is not a one to one funcction.
Question 2: Is function g defined by


g = {(-1 , 2),(0 , 4),(2 , -4),(5 , 6),(10 , 0)}
,

a one to one function?
Solution to Question 2 :


Consider any two different values in the domain of function g and check that their corresponding output are different. Hence function g is a one to one function
  • Question 3: Is  faction f given by



    f(x) = -x 3 + 3 x 2 - 2
    ,

    a one to one function?
    Solution to Question 3:
    • A graph and the horizontal line test can help to answer the above question.

      graph of function f in question 3

      Since a horizontal line cuts the graph of f at 3 different points, that means that they are at least 3 different inputs x1, x2 and x3 with the same output Y and therefore f is not a one to one function.
    • Question 4: Show that all linear functions of the form


      f(x) = a x + b
      ,

      where a and b are real numbers such that a not equal to zero, are one to one functions.
      Solution to Question 4:
      • We start with f(A) = f(B) and show that this leads to a = b

        a(A) + b = a(B) + b
      • Add -b to both sides of the equation to obtain

        a(A) = a(B)
      • Divide both sides by a since it is not equal to zero to obtain

        A = B
      • Since we have proved that f(A) = f(B) leads to A = B then all linear functions of the form f(x) = a x + b are one-to-one functions.

        A = B  
                              Good evening to everyone.

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