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Finding domain of a function without knowing its graph

Type I. There is no restriction on the inputs.

For example, f(x)=ax2+bx+c (quadratic function or any polynomial functions), tex2html_wrap_inline46 (absolute function), f(x)=mx+b. The domain of the function is all real numbers.

Type II. Fractional functions

Example: If tex2html_wrap_inline50 the domain of f = all reals tex2html_wrap_inline56 the reason is that the input (x) can't be 1 or tex2html_wrap_inline62

Exercises. Find the domain of the following functions:

  1. tex2html_wrap_inline64 [all reals except x=-1, 3]
  2. tex2html_wrap_inline70 [all reals except tex2html_wrap_inline72 -1].

Type III. Radical functions

Example: If tex2html_wrap_inline76 find the domain of f. The key is that the quantity inside the even radical should be positive, i.e. tex2html_wrap_inline80 which amounts to solve an inequality. (so you need to review techniques of solving inequalities.) Dom (f) tex2html_wrap_inline84

Example: If tex2html_wrap_inline86 then find the domain of f. There are two restrictions on f, one is from the sqare root, tex2html_wrap_inline92 and tex2html_wrap_inline94 Thus the domain of f tex2html_wrap_inline98

Exercises: Find the domain of the following functions:

  1. tex2html_wrap_inline100
  2. tex2html_wrap_inline102
  3. tex2html_wrap_inline104

Horizontal and Vertical Shiftings

Horizontal Shifting:

Note that y=f(x+a) is a horizontal shifting of y=f(x).

Example: Note that tex2html_wrap_inline110 is a horizontal shifting of f(x)=x2, tex2html_wrap_inline114 is shifted to the right one unit from y=x2.

Vertical Shifting:

Note that y=f(x)+a is a vertical shifting of y=f(x). If a>0, then it is shifted up, and if a<0, the graph is shifted down.

Example: Note that tex2html_wrap_inline126 is shifted down 2 units from tex2html_wrap_inline130

Exercises: Use the shifting techniques to sketch the graph of the following functions:

  1. tex2html_wrap_inline132
  2. tex2html_wrap_inline134
  3. tex2html_wrap_inline136