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


X-12=-4
x=-4+12
x=8
The answer is A
Answer:
Solution (7,1)
Step-by-step explanation:
Use the elimination method
x + y=8
x - y=6
--------------Add
2x = 14
x = 7
Substitute x = 7 into x + y=8
7 + y=8
y = 8 - 7
y = 1
Solution (7,1)
Answer:
64
is the answer please mark me brainlest