Answer:

Step-by-step explanation:
The point at the terminal side of an acute angle is given by
.
That is,
and
.
Let r be the length of line segment drawn from the origin to the point and is given by the formula:

Substituting the values of x and y into r,



Thus,
Also,
is given by:

Substituting values of x and r,

Is it 2 times x squared (2x^2?
2 * 6^2
2 * 36
72
Sn=A1(1-r^n)/(1-r)
Sum of a finite geometric series formula
We know the sum, number of terms and rate, so you plug those in.
-255=A1(1-(-4)^4))/(1-(-4)
-255=A1(1-256)/5
-255=A1(-255)/5
-1275=A1(-255)
5=A1
Hope this helped! Let me know if you have any questions.