# OCR A Level Mathematics B (MEI) Paper 3 (H640/03) - 20th June 2024 [Exam Chat]

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There are normally a few pretty simple marks you can get from section B without even bothering to read the insert in any depth (but give it a skim read for a minute or do anyway). I’d be inclined to get them out of the way and then head back to section A.
guys can someone please explain how to do part (ii) of this question

how do you find the minimum values of a and b?
(edited 1 month ago)
Have we had any questions on R formulae? i cant remember
uhh thats a mean one! took me a while. i think find the midpoint of BC as thats the only side we know, then use the other triangle formula for a RAT which is 0.5xbxh to get an expression where you will see that (a-2.5)^2, so for it to be minimum im guessing a = 2.25 so then the bracket = 0? then sub back in to get b. lmk if youre still stuck and i can help
(edited 1 month ago)
Original post by laauureenamber
uhh thats a mean one! took me a while. i think find the midpoint of BC as thats the only side we know, then use the other triangle formula for a RAT which is 0.5xbxh to get an expression where you will see that (a-2.5)^2, so for it to be minimum im guessing a = 2.25 so then the bracket = 0? then sub back in to get b. lmk if youre still stuck and i can help

Haven’t checked your working but the method looks right. Could also differentiate and even find the second derivative to check it’s a min, but possibly overkill.
Original post by T!gger34
Haven’t checked your working but the method looks right. Could also differentiate and even find the second derivative to check it’s a min, but possibly overkill.

honestly that would still work but i tried that first as i thought that was what it was asking and it wasnt as pretty aha and i couldnt get the right answer but that was probably just me
Original post by laauureenamber
honestly that would still work but i tried that first as i thought that was what it was asking and it wasnt as pretty aha and i couldnt get the right answer but that was probably just me

Agreed. Well done for fathoming it out.
What do u guys think r likely topics?
Original post by user_29
What do u guys think r likely topics?

trig hasnt come much in the other two papers so maybe the insert is based on trig???
Original post by laauureenamber
uhh thats a mean one! took me a while. i think find the midpoint of BC as thats the only side we know, then use the other triangle formula for a RAT which is 0.5xbxh to get an expression where you will see that (a-2.5)^2, so for it to be minimum im guessing a = 2.25 so then the bracket = 0? then sub back in to get b. lmk if youre still stuck and i can help

heyy thank you so much for replying! i'm super sorry but i still don't fully get it ( here's what i did and i would be super grateful if you could explain how i should continue!
thankssx
Original post by navvvv
heyy thank you so much for replying! i'm super sorry but i still don't fully get it ( here's what i did and i would be super grateful if you could explain how i should continue! thankssx

i think where youve got yourself stuck is that you can write AD in terms of just "a" rather than a and b. AD should be 3-a i + 2-aj + 1k (in unit notation cant do column here haha) so then your area will be the same just in terms of a. next you need to complete the square to get root 3 x root(2(a-2.5)^2+0.75) then you can see that a must be 2.5 in order for that bracket = 0.

just to clarify: you will have (3-a)^2 + (2-a)^2 + 1 in your square root, just expand this and collect like terms, then complete the square
(edited 1 month ago)
Spot on.👍
Original post by laauureenamber
i think where youve got yourself stuck is that you can write AD in terms of just "a" rather than a and b. AD should be 3-a i + 2-aj + 1k (in unit notation cant do column here haha) so then your area will be the same just in terms of a. next you need to complete the square to get root 3 x root(2(a-2.5)^2+0.75) then you can see that a must be 2.5 in order for that bracket = 0.
just to clarify: you will have (3-a)^2 + (2-a)^2 + 1 in your square root, just expand this and collect like terms, then complete the square

omg right!! the previous subsection (i) was to show that a-b+1=0, i guess i forgot that i should be using the previous answers for the follow up. this explanation was very helpful, thank you so much!!
Anyone thinking of resorting any exam ?
how did everyone find it
that comprehension section was so stupid
Original post by shkshjsdh
how did everyone find it
Cl pure was calm but did you even understand what the comprehension section was asking? I only got the first two substitutions
The pure section was good but I think I got 6/15 on the comprehension it was so confusing
What the **** was that paper
What did people get for x coordinate where gradient = 1??