Question

What is the domain and range for the following function and its inverse?

Answer 1

Answer:

Step-by-step explanation:

The domain of that function is all real numbers.  The x values will drop into negative infinity and will grow to positive infinity.

The range is found from the vertex form of a parabola, which is

$y=(x-h)^2+k$

where h indicates side to side movement of the vertex and k indicates up or down.  Our function has a +3 at the end of it and is positive (so it opens upwards), so the range is y ≥ 3.

To find the inverse of that function, switch the x and y coordinates and solve for the new y.  Let f(x) be y, then switch the x and y:

$x=y^2+3$

Now solve for the new y:

y = ±$\sqrt{x-3}$

To find the domain of a radical, set the radicand greater than or equal to 0 and solve for x (this is because the radicand cannot be a negative number or we are dealing with imaginary numbers and that's not what you want.  BTW, a radicand is the term under the radical sign).  

x - 3 ≥ 0  so   x ≥ 3.  The domain of the inverse is all real numbers greater than or equal to 3.

This is a sideways parabola (the inverse is), and it opens to the right starting at the x value of 3.  It will grow into positive values of y to infinity and will drop into negative values of y into negative infinity.

Just a little trick here to remember, and it ALWAYS holds true:  the domain of a function is the range of its inverse, and the range of a function is the domain of its inverse.  Look to our solution for your problem here and you'll see that it is true.