Answer:
see the explanation
Step-by-step explanation:
we have

we know that
The radicand of the function cannot be a negative number
so

Solve for x
Multiply by -1 both sides

The domain of the function f(x) is the interval -----> (-∞, 0]
The domain is all real numbers less than or equal to zero
The range of the function f(x) is the interval ----> [0,∞)
The range is all real numbers greater than or equal to zero
<em>Example</em>
For x=144
----> is not true
This value of x not satisfy the domain
substitute
----> this value is undefined
For x=-144
----> is true
This value of x satisfy the domain
substitute
----> this value is defined
therefore
The function will be undefined for all those values of x that do not belong to the interval of the domain of the function
profit=f(x)
so solve for f(x)=1000
1000=70n-400
add 400 to both sides
1400=70n
divide both sides by 70
20=n
20 students need to be enrolled to make a profit of 1000.00