What is the domain and range of f(x) = -7(x - 2)^2 - 9f(x)=7(x2)29?

1 Answer
May 5, 2018

See below.

Explanation:

-7(x-2)^2-97(x2)29

This is a polynomial, so its domain is all RR.

This can be expressed in set notation as:

{x in RR}

To find the range:

We notice that the function is in the form:

color(red)(y=a(x-h)^2+k

Where:

bbacolor(white)(88)is the coefficient of x^2.

bbhcolor(white)(88) is the axis of symmetry.

bbkcolor(white)(88) is the maximum or minimum value of the function.

Because bba is negative we have a parabola of the form, nnn.

This means bbk is a maximum value.

k=-9

Next we see what happens as x-> +-oo

as x->oo , color(white)(8888)-7(x-2)^2-9->-oo

as x->-oo , color(white)(8888)-7(x-2)^2-9->-oo

So we can see that the range is:

{y in RR | -oo < y <= -9}

The graph confirms this:

graph{-7x^2+28x-37 [-1, 3, -16.88, -1]}