APEX ! Non-linear systems of equation.
It is 5:9 in simplest form
an = a1r^(n-1)
a5 = a1 r^(5-1)
-6 =a1 r^4
a2 = a1 r^(2-1)
-48 = a1 r
divide
-6 =a1 r^4
---------------- yields 1/8 = r^3 take the cube root or each side
-48 = a1 r 1/2 = r
an = a1r^(n-1)
an = a1 (1/2)^ (n-1)
-48 = a1 (1/2) ^1
divide by 1/2
-96 = a1
an = -96 (1/2)^ (n-1)
the sum
Sn = a1[(r^n - 1/(r - 1)]
S18 = -96 [( (1/2) ^17 -1/ (1/2 -1)]
=-96 [ (1/2) ^ 17 -1 /-1/2]
= 192 * [-131071/131072]
approximately -192
Let the balance = Y and the number of weeks = x
She takes out 15 per week, so multiply 15 by x ( the number of weeks) to get 15x.
You would then want to subtract that from the amount she started with in her account.
The equation becomes: Y = 150 - 15x
I am not sure if you have any choices. Here are some options:
0.17333333333
This is also notated by .1733 with a line over the top of the two 3's indicating that these number continue repeating.
Other choices depending on your instructions...
.173 (if rounded to thousanths)
.17 (if rounded to hundreths)
.2 (if rounded to tenths)
