Step-by-step explanation:
a(n) = a +(n-1)d
a=13
d=9-13=5-9=-4
°.° a(n) = 13 +(n–1)-4
hope this helps
Answer:
157.5 is the answer
Step-by-step explanation:
K-10=-7
K=10-7 Add 7 for both side.
k=3
Answer:

Step-by-step explanation:
Given

Required
Determine 

Open bracket

Equate the equation to 0

Express 3 as 1 + 1 + 1

Collect like terms

Group each terms

Factorize (starting with the first bracket)












Express 0 as 0 + 0 + 0

By comparison



Solving for 
Take square root of both sides

Add 1 to both sides


Solving for 
Take square root of both sides

Subtract 1 from both sides


Solving for 
Take square root of both sides

Subtract 1 from both sides


Substitute the values of a, b and c in 


