Lesson Plan

Identify a geometric series and state the first term, common ratio, and number of terms

Derive the formula S = a(1 - r^n)/(1 - r) using the multiply-and-subtract technique, and explain each step of the derivation

Apply the formula to compute the sum of any finite geometric series where r != 1

Handle the special case r = 1 correctly (sum = na) and explain why the main formula cannot be used when r = 1

Solve real-world problems (savings plans, loan payments, repeated geometric growth) using the geometric series formula

HSA.SSE.B.4

HSA.SSE.B.4: Derive the formula for the sum of a finite geometric series (when the common ratio is not 1), and use the formula to solve problems. For example, calculate mortgage payments.