A(n)=4+4(n-1)
a(n)=4+4n-4
a(n)=4n
76=4n
n=19
The sum of any arithmetic sequence (series are infinite) is:
(a+a(n))(n/2)
The average of the first and last terms times the number of terms, in this case we found that n=19 so:
19(4+76)/2=760
The angle here is an acute angle at ground level. Then the side adjacent to this angle is 126 feet. The opp. side is the tower, 111 feet tall.
Then
tan theta = opp / adj = 111 / 126. Using the inverse tangent function, we find that the measure of the angle is 0.722 radian or 41 degrees (to the nearest degree).
Your sequence appears to be geometric with a common ratio of 2. It can be described by
a(n) = (-2 2/3)·2^(n-1)
_____
This can be written in a number of other forms, including
a(n) = (-8/3)·2^(n-1)
a(n) = (-1/3)·2^(n+2)
a(n) = (-4/3)·2^n
For this case, the first thing we must do is define variables:
x: unknown number (1)
y: unknown number (2)
We now write the equations that model the problem:
their sum is 6.1:

their difference is 1.6:

Solving the system we have:
We add both equations:

Then, we look for the value of y using any of the equations:
Answer:
The numbers are:
Where is the grid are u gonna take a pic?