5.3 Sum of First n Terms (Sn)

Ask AI

Key Formulas

Solved Examples

Step 1

Identify a=8a=8, n=22n=22, d=3−8=−5d = 3 - 8 = -5[cite: 1194].

Step 2

Use Formula B: S22=222[2(8)+(22−1)(−5)]S_{22} = \frac{22}{2}[2(8) + (22-1)(-5)].

Step 3

S22=11[16+21(−5)]S_{22} = 11[16 + 21(-5)].

Step 4

S22=11[16−105]=11[−89]S_{22} = 11[16 - 105] = 11[-89].

Step 5

S22=−979S_{22} = -979[cite: 1197].

Final Answer

-979

Interactive Solver