Here we're discussing the "nth partial sum of a geom series."
1 - r^n
The formula for that is s(n) = a(1) ---------------
1-r
We can subst. the given values and see where that takes us:
1 - (-2)^6 1 - 64
105 = a(1)*---------------- = ----------*a(1) = -21*a(1)
1-(-2) 3
105
Solving this for a(1): a(1) = --------- = -5 (answer)
-21
17(n+31)=357
distribute:
17n+527=357
-527 -527
17n= -170
÷17 <span>÷17
</span>n=-10
A: negative 10
You have 2 denominators so they need to be in the same family 5 and 10 are in the same family you take the biggest denominator and that is your common denominator and 3 + 1 =4 so 4/10 is your answer. (unless you need to simplify)
and inner radius 
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