Each step adds exactly 4 to the previous term. This is your common difference (d).
To reach the nth term, you take (n-1) steps from the starting height 3.
FENCE POST TRAP: Don't take n steps! The first term is already at position 1, so you only need (n-1) jumps.
KEY FORMULA:
u_n = 3 + (n-1) × 4
🔧 The Simultaneous Equation Solver
Given Information:
Cambridge Mark Scheme Working:
Step 1: Write equations
a + 4d = 19
a + 1d = 7
Step 2: Subtract equations
3d = 12
d = 4.0
Step 3: Substitute back
a + 4 × 4.0 = 19
a = 3.0
Final Formula:
u_n = 4.0n + -1.0
THE SIMULTANEOUS TRAP:
When given two non-consecutive terms (like u₅ and u₁₀), you MUST write two equations in terms of a and d, then solve simultaneously. Students often try to "guess" the pattern - this loses ALL working marks. Always show the subtraction step to find d first!
Sign In to Keep Going
You've reached the end of the free preview. Sign in — and upgrade to Plus or Pro — to keep going with Math4MA1.