You want to show that the solution of T(n) = T(n − 1) +n is O(n²), using
the substitution method. If you plug in recursively, any large C' value will work
within the standard inductive proof, but very small C' values will not work.
The largest C' value that fails within the proof is
If you use C = .75, the smallest no value that you can use that will make the
inductive equation work is
(Note, it is not an integer.)
In both cases, writing the value as a decimal number is probably your best bet,
formatting-wise.
Fig: 1