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Your result · Integration by substitution (Q3b)
5/6
Edexcel A-level Maths · marked by Jodie McNaught · returned in 4 hours
Where each mark went
Correct substitution u = 2x+1 stated
Correct integral expression in terms of u
Integration carried out correctly
Correct expression before back-substitution
Correct final answer in terms of x
+C omitted from final answer
This is the 2nd time this term. One mark every time — we’re fixing this today.
Your answer vs A*
Your answer
u = 2x+1, du = 2dx
∫(2x+1)³ dx = ∫u³ · du/2
= u⁴/8
= (2x+1)⁴/8
← missing +C
A* answer
u = 2x+1, du = 2dx
∫(2x+1)³ dx = ∫u³ · du/2
= u⁴/8
= (2x+1)⁴/8
+ C ✓
One line separates 5/6 from 6/6 — every indefinite integral ends with +C.
Jodie McNaught
Senior Edexcel Maths Examiner · personal note · 68s
“Aiden — 5/6, a genuine improvement. The method is completely sound. I’m going to keep saying +C until it’s automatic for you, because after that this topic is done. Here’s exactly what I need you to do today…”
3 actions · do these today
“The method is genuinely there. You’re one habit away from full marks. Here’s exactly what I want you to do:”
Write “+ C” before you write anything else on every indefinite integral
Not because you don’t know it — your working shows you apply it then drop it at the end. One line at the top forces the habit. Every time, no exception.
Attempt Q5 from the 2022 Paper 2 — indefinite integrals
Same structure as what you just submitted. When you reach the final answer: stop, write + C, then submit. I’ll mark it today.
Watch the +C clip from the integration masterclass — bookmarked at 12:04
I show exactly where students drop this mark using two real scripts side by side. Three minutes that fixes it permanently.
Ed
personal context
This is the 3rd time +C has appeared in your FeedForward. Mark's first action takes 2 minutes — do it now. Your GenieScore updates to 72 once all 3 actions are marked done — that's A-grade territory.
Next step
2022 Paper 2 Q5 is ready for you
Same structure as what you just submitted. Jodie will mark it within 24 hours — this is how the +C habit gets fixed permanently.