Question

Solve the formula for a

Answer 1

`\\ \tt\longmapsto S=(a(1-r^n))/(1-r)`

• Use cross multiplication

`\\ \tt\longmapsto S(1-r)=a(1-r^n)`

`\\ \tt\longmapsto a=(S(1-r))/(1-r^n)`

Answer 2

Given formula:

• 
  `S = a(1-r^n)/(1-r)`

Solving for a:

• 
  `S(1-r) = a(1-r^n)`
• 
  `a = S(1-r)/(1-r^n)`