Do you need an explanation of the work shown? The distance can be found by multiplying the rate by the time. as long as you know two of three parts, you can find the missing value. There is no problem shown in the picture?
Found this on socratic !!! hope this helps !!!!
Given:
The function is:

To find:
The domain of the given function.
Solution:
Domain is the set of input values.
We have,

It is a quadratic polynomial.
We know that a quadratic polynomial is defined for all real values of x. So, the given function is defined for all real values of x and the domain of the given function is:
Domain = Set of all real number
Domain = (-∞,∞)
Therefore, the correct option is B.
Answer:
It would be D because X^2 is different from 3x you would just multiply X^2 by 1 and 3x by 1 to get x^2+3x