f(x)=sqrt(x+4)
also one that is divided
f(x)=2x+1/x-3
I have a whole page of them but if I have a couple of examples I can figure it out from there.
Answers:
The domain is the possible values that you can plug in for x.
f(x)=sqrt(x+4)
Recall that you cannot take the square root of negative numbers.
Therefore, whatever is under the square root symbol must be greater than or equal to zero.
x + 4 >= 0
Subtract 4 from each side.
x >= -4
The domain is all real numbers greater than or equal to -4.
f(x)=2x+1/x-3
I'm assuming that the whole quantity (x-3) is in the denominator. It should be written like this.
f(x)=2x+1/(x-3)
You cannot divide by zero, so x - 3 cannot equal zero. Find what value makes x-3 equal to zero, and exclude this from the domain.
x - 3 = 0
Add 3 to each side
x = 3.
The domain is all real numbers except -3.
Edit: I looked at your question in the math section.
f(x)=3x^2+5x-3
The domain of a polynomial is always all real numbers. (Polynomials don't involve any variables in the denominator or underneath a root symbol).
finding the domain is actually finding the solution
first one
make f(x) to 0
square both sides
0 = (x+4)
x = -4
second one
make f(x) to 0
multiply all terms by x
0 = 2x^2 + 1 + 3x
2x^2 + 3x + 1
(2x +1)(x+1)=0
x = -1/2, x = -1
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