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.

Launch All 6 Active-Recall Cards
CARD 1 OF 6 • THE CLASSROOM TIME TRAP (150s)
Why Students Bleed Time:
Writing out the binomial expansion terms up to r=3r = 3 takes ~135s. The general term is Tr=(6r)(2)6−r(−1)rx1(6−r)−1rT_r = \binom{6}{r}(2)^{6-r}(-1)^r x^{1(6-r) - 1r}. Setting the exponent to 00 gives r=3r = 3, yielding 20×8×(−1)=−16020 \times 8 \times (-1) = -160.
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 1(6−r)=1r  ⟹  r=31(6 - r) = 1r \implies r = 3 in 5s.
Line 2 (Isolate Single Term): (63)(2)3(−1)3=20×8×(−1)=−160\binom{6}{3}(2)^{3}(-1)^{3} = 20 \times 8 \times (-1) = -160 (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.

Open Sign / Direction Flip Clinic
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.

Open Factor-of-2 / Stoichiometry Clinic
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.

Open Intermediate Stop Trap Clinic
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.

Open Fence-Post / Domain Trap Clinic

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.

sub90 ESAT Stopwatch Emblemsub90 ESAT
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
Question 1 of 1ARCH-MM-13 (6-Card Lesson)Format: Standard 5-Option
Right-click any option to cross out • Keys A–E + Enter
Question 1 of 1 • 90s Target

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The question stem, diagram, and answer options are hidden behind this pre-start gate. When you click below, the question will reveal and your 90-second split stopwatch will immediately begin ticking.

Mathematics 2•ARCH-MM-13•Standard 5-Option
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