Answer: 1
Step-by-step explanation:
The formula for calculating the sum of a Geometric series if the common ratio is greater than 1 is given as :
= 
Where is the sum of terms , a is the first term , r is the common ratio and n is the number of terms.
From the question:
= 3280
a = ?
r = 3
n = 8
Substituting this into the formula , we have
3280 = 
3280 = 
Multiply through by 2 , we have
6560 = a ( 6560)
divide through by 6560, we have
6560/6560 = a(6560)/6560
Therefore : a = 1
The first term of the series is thus 1
Answer:
b A train backed up 7 feet and then moved
forward 7 feet.
Answer:
Converting the equation 
into completing the square method we get: 
Step-by-step explanation:
we are given quadratic equation:
And we need to convert it into completing the square method.
Completing the square method is of form: 
Looking at the given equation
We have a = x
then we have middle term 20x that can be written in form of 2ab So, we have a=x and b=? Multiplying 10 with 2 we get 20 so, we can say that b = 20
So, 20x in form of 2ab can be written as: 2(x)(10)
So, we need to add and subtract (10)^2 on both sides
So, converting the equation into completing the square method we get:
B, because every prime number greater than 2 is odd, and the product of two odd numbers is odd.
