Answer:
f(x) = 17x +17
136 in
Step-by-step explanation:
Changing the number of boxes by 1 changes the stack height by 17 inches, so the arithmetic sequence can be written as
... f(x) = x₁ +d(x -1)
The first term is shown to be 34, so the function is
... f(x) = 34 +17(x -1)
This can be simplified to ...
... f(x) = 17x +17
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From 1 box to 4 boxes (addition of 3 boxes), the height changed from 34 in to 85 in (addition of 51 in).
Adding 3 more boxes to make 7 boxes in the stack should add 51 more inches:
... 85 in + 51 in = 136 in
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The problem statement tells you to use the above function to solve the problem, so ... (put 7 where x is, then do the arithmetic)
... f(7) = 17·7 +17 = 119 +17 = 136 . . . inches
