Answer:


Step-by-step explanation:
Given


Solving (a): T7
Substitute 7 for n in 


Calculate S7 and S6



So:


Solving (b): Tn

Where 
Calculate
We have:

Open brackets



So:



Collect Like Terms


The midpoint would be (5,9)
Answer:
b
Step-by-step explanation:
Answer: AC=12 cm
Step-by-step explanation:
To solve this problem you must apply the law of sines, as you can see below:

Where:
a=13
A=85.2°
B=71.6°
Therefore, you must solve for b, then, you obtain that the lenght AC asked in the problem above is:

Answer:
12.12%
Step-by-step explanation:
We have that the formula is given by:
A = p * e ^ (r * t)
From here, we know that A = 200000; p = 20000 and the time we can calculate 40 - 21 = 19
if we replace we have:
200000 = 20000 * e ^ (19 * r)
we must calculate r:
e ^ (19 * r) = 200000/20000
e ^ (19 * r) = 10
19 * r = ln 10
r = ln 10/19
r = 0.1212
In other words, the rate of growth is 12.12%