Answer:
x ∈ (-∞ , -2) ∪ (1, 3)
Step-by-step explanation:
The expression is already factored. Note that for the polynomial that appears in the numerator 
there are 2 roots:
For the polynomial that appears in the denominator there is 1 root:
Note that does not belong to the domain of f(x) because it zeroes the denominator of the function and the division between zero is not defined.
With these three roots we do the study of signs to find out when 
Observe the attached image
Note that:
when 
when 
when 
Finally, we have the solution:
x ∈ (-∞ , -2) ∪ (1, 3)
If I’m correct this is supposed to be a decimal ( here we use the dot not the comma ) but if so then 32.52 a good way to remember is 5 or more let it sore (meaning round up) four or less let it rest (meaning it stays the same)
So to set up this equation, you have to do
Time1*Workers1=Time2*Workers2
In this case, Time1=24 days, Workers1=15 electricians, and Workers2=18 electricians, and we have to solve for Time2
Thus we get 15*24=18*Time2
Time2=15*24/18=20 days
