Topic explanation

Standard explanation

d = a2-a1 = a3-a2. If the differences are not equal, it is not an AP. 3, 3, 3, ... is an AP with d=0.

Key points

• subtract neighbours
• common difference d
• a_n = a + (n-1)d
• n-1 jumps
• COMMON DIFFERENCE: d = a2-a1 = a3-a2. If the differences are not equal, it is not an AP. 3, 3, 3, ... is an AP with d=0
• COMMON DIFFERENCE: d = a2-a1 = a3-a2.
• WHAT — COMMON DIFFERENCE: d = a2-a1 = a3-a2. If the differences are not equal, it is not an AP. 3, 3, 3, ... is an AP with d=0
• WHY — Why it matters: This rule is a separate learning unit inside arithmetic sequence. It can be defined, applied, and ch

Labelled diagram