Explain the meaning of -500 in context to the problem

Find the average rate of change for f(x) = x2 − 3x − 10 from x = −5 to x = 10.

Can someone check if i did this correct. it’s number 4 if you’re wondering.

Acable company claims that the average household pays $78 a month for a basic cable plan, but it could differ by as much as $20. write an absolute value inequality to determine the range of basic cable plan costs with this cable company. a. |x − 78| ≥ 20 b. |x − 20| ≥ 78 c. |x − 20| ≤ 78 d. |x − 78| ≤ 20