Question

A cable 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

Answer 1

Answer is B cause you have to minus the 20 then then swap the signs

Answer 2

D. |x − 78| ≤ 20

Explanation:

Given,

The monthly charges for a basic cable plan = $ 78,

Also, it could differ by as much as $20,

So, the maximum charges = $(78 + 20) ,

And, the minimum charges = $(78 - 20),

Let x represents the monthly charges ( in dollars ),

78 - 20 ≤ x ≤ 78 + 20

⇒ 78 - 20 ≤ x and x ≤ 78 + 20

⇒ -20 ≤ x -78 and x-78 ≤ 20

⇒ 20 ≥ -(x-78) and x-78 ≤ 20 ( ∵ a > b ⇒ -a < -b )

⇒ |x-78| ≤ 20

Which is the required absolute value inequality to determine the range of basic cable plan costs,

Option 'D' is correct.