At the end of the 6 months the balance would be 360.54
0.875 is the density for this question
The function in vertex form is

(refer to your other post I solved it there).
The general form of quadratic equations in vertex form is

, where (h, k) is the vertex of the parabola.
Here, a = 1, h = -6 and k = -54
Therefore, the vertex is (-6, -54) and it is a maximum because a = 1 is postive.
Answer:
yes
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you can look at 3:3 as 3/3 which is 1
and 1:1 = 1/1 which is also 1
the ratio sign also means divide.
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hope this helps :)