B. The rational expression is not defined for any values of

20^2-180/4x^2+36+ 72

for which the denominator equals zero. Find the value(s) of for which the denominator equals zero.

so, just solve

4x^2 + 36x + 72 = 0
x^2 + 9x + 18 = 0
That should help...

C. The company accountant says that the rational expression will never have a zero denominator because , the number of units, is always a whole number. Explain why the accountant is correct.

20^-180/4^2+36x+72

this is the second part can you help me

I have no idea .

To find the values for which the denominator of the rational expression equals zero, we need to solve the equation:

4x^2 + 36x + 72 = 0

Let's solve this quadratic equation:

First, we can divide the whole equation by 4 to simplify it:

x^2 + 9x + 18 = 0

Now, we can factorize the quadratic equation:

(x + 3)(x + 6) = 0

By using the zero product property, we can set each factor equal to zero and solve for x:

x + 3 = 0 --> x = -3
x + 6 = 0 --> x = -6

Therefore, the values of x for which the denominator equals zero are x = -3 and x = -6.