UAT-UK SPEC CODE: MM2 (Sequences and series)ASSUMED MATHS 1 PREREQUISITE: M4.1FREQUENCY: VERY HIGH
Binomial Expansion (a + bx)^n Term Isolation, Constant Terms & Multi-Bracket Coefficients
Deconstructed from 34 past UAT-UK questions (8.29% of all historical Mathematics 2 papers). Students using standard A-Level classroom methods spend an average of 150s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 40s (saving 110s per question).
Historical Frequency
34 Past Qs
8.29% of Mathematics 2
Classroom Trap Time
150s
+60s over 90s budget
Sub-90 Target Time
40s
Banks +110s on the clock
Dominant UI Format
5-Option A–E
Maths 1 Skill: M4.1
Card 1 & Card 2 Preview: The Classroom Time Trap vs. Sub-90 2-Line Rule
Excerpted from our interactive 6-Step Topic Lesson for ARCH-MM-13.
CARD 1 OF 6 • THE CLASSROOM TIME TRAP (150s)
Why Students Bleed Time:
Writing out the binomial expansion terms up to takes ~135s. The general term is . Setting the exponent to gives , yielding .
In 34 past UAT-UK questions (8.29% of Mathematics 2), candidates lose 110s by treating the minus sign as positive for odd powers r in ncr * a^(n-r) * (-bx)^r. Instead, apply MM2 with Maths 1 skill M4.1.
CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<40s)
Line 1 (Zero-Exponent Index): Solve in 5s.
Line 2 (Isolate Single Term): (30s).
Sanity & Limit Check: Verify units/signs against
sign_or_direction_flip (Dropping (-1)^r when expanding (a - bx)^n) and factor_of_two_or_stoichiometry_trap (Writing nCr * a^(n-r) * b * x^r instead of nCr * a^(n-r) * b^r * x^r).Examiner Distractor Blueprint for ARCH-MM-13
FOIL #1sign_or_direction_flip
Dropping (-1)^r when expanding (a - bx)^n
Treating the minus sign as positive for odd powers r in nCr * a^(n-r) * (-bx)^r.
FOIL #2factor_of_two_or_stoichiometry_trap
Writing nCr * a^(n-r) * b * x^r instead of nCr * a^(n-r) * b^r * x^r
Failing to raise the coefficient b (or 1/b) to the power r.
FOIL #3intermediate_stop_trap
Computing only one cross-product term instead of all pairs (e.g. 1*x² + x*x + x²*1) in (1+ax+bx²)(1+cx)^n
Forgetting to sum all index combinations from both brackets that add to the target power.
FOIL #4fence_post_or_domain_trap
Using r = k instead of solving p*(n - r) + q*r = k for expansions of (a*x^p + b*x^q)^n
Assuming the r-th term has power x^r when both terms inside the bracket contain powers of x.
Try 1 Live Sample Question Under the 90-Second Stopwatch
Press W to open the 2-line dry-wipe scratchpad, select A–E, and lock in to reveal the Dual-View solution.
ARCH-MM-13: Binomial Expansion (a + bx)^n Term Isolation, Constant Terms & Multi-Bracket Coefficients (Sample)Mathematics 2
00:00.0
SUB-90 ZONE (<40S)
0.0s40s Sub-9090s ESAT Budget150s Classroom
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A–E + EnterQuestion 1 of 1 • 90s Target
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Mathematics 2•ARCH-MM-13•Standard 5-Option
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