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    Show that the substitution y =vx, where v is a function of x, transforms the differential equation

    xy.dy/dx = x^2 + y^2

    into the differential equation

    vx.dv/dx = 1

    Stuck, help! Q 52 review exercise 2 of the p3 book ...
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    (Original post by imasillynarb)
    Show that the substitution y =vx, where v is a function of x, transforms the differential equation

    xy.dy/dx = x^2 + y^2

    into the differential equation

    vx.dv/dx = 1

    Stuck, help! Q 52 review exercise 2 of the p3 book ...
    hi
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    ****, so close, I differentiated y = vx wrongly ;(
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    bloody hell thats a hard question... hope to god i don't get anything like that in my exam! what board are you guys on?
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    (Original post by wibble...)
    bloody hell thats a hard question... hope to god i don't get anything like that in my exam! what board are you guys on?
    edexcel.

    in fact, using substituition to simplify a SECOND order differential equation is p4.

    you'll be fine, trust me
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    (Original post by kikzen)
    edexcel.

    in fact, using substituition to simplify a SECOND order differential equation is p4.

    you'll be fine, trust me
    im OCR/MEI and have never seen anything as hard as that... i seriously would be buggered if i had anything like that!
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    (Original post by wibble...)
    bloody hell thats a hard question... hope to god i don't get anything like that in my exam! what board are you guys on?
    Its differentiating parametrics. Though the ones you have/will come across won't be more than two variables (upto P3).
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    (Original post by wibble...)
    im OCR/MEI and have never seen anything as hard as that... i seriously would be buggered if i had anything like that!
    Buggery is a crime.
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    On OCR that's P4!
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    (Original post by fishpaste)
    On OCR that's P4!
    seriously??? oh thank god!! i can breath again now!
    oh and to bhaal.... ehh???!!
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    (Original post by wibble...)
    seriously??? oh thank god!! i can breath again now!
    oh and to bhaal.... ehh???!!
    Nothing, I'm just procrastinating, as I should really be revising for P3, Wednesday is it? Have you done any past papers yet, stuck on anything?
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    (Original post by imasillynarb)
    Show that the substitution y =vx, where v is a function of x, transforms the differential equation

    xy.dy/dx = x^2 + y^2

    into the differential equation

    vx.dv/dx = 1

    Stuck, help! Q 52 review exercise 2 of the p3 book ...
    From P3 principles I can do that question.
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    iv got mech1 this weds and p3 the following weds... iv been doing loads of past papers... getting stuck on quite a few things! yea that question is technically do-able from what i know but i still think i wouldn't manage it in my exam!
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    (Original post by wibble...)
    iv got mech1 this weds and p3 the following weds... iv been doing loads of past papers... getting stuck on quite a few things! yea that question is technically do-able from what i know but i still think i wouldn't manage it in my exam!
    I have exactly the same. I've done so much P3 revision and I'm finding it A LOT easier than M1. Can't stand Mechanics!
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    (Original post by Emma Louise)
    I have exactly the same. I've done so much P3 revision and I'm finding it A LOT easier than M1. Can't stand Mechanics!
    i find m1 soooo much easier than p3!! il gladly help wiv any problems you have!
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    (Original post by wibble...)
    i find m1 soooo much easier than p3!! il gladly help wiv any problems you have!

    nah M1 is the easiest out of all maths topics i got 88% on that, i loved M1 M2 is a bit harder tho.
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    (Original post by wibble...)
    i find m1 soooo much easier than p3!! il gladly help wiv any problems you have!
    Thanks I shall keep that in mind (considering there's only a few days)! The main problem is with the M1 textbook. I swear most of the answers in the back are wrong. Not only that but the worked examples aren't even correct. Stress!
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    (Original post by lexazver203)
    nah M1 is the easiest out of all maths topics i got 88% on that, i loved M1 M2 is a bit harder tho.
    i will be very disappointed if i don't get a good A in m1... hopefully it will make up for my unbelievably poor p3 results! i have heard that as generally most people don't do too well in p3 they lower the grade boundaries (ie less marks needed to get better grades) is this true? if so does anyone know what these boundaries are likely to be?
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    (Original post by Bhaal85)
    Buggery is a crime.
    Not any more.
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    (Original post by wibble...)
    i will be very disappointed if i don't get a good A in m1... hopefully it will make up for my unbelievably poor p3 results! i have heard that as generally most people don't do too well in p3 they lower the grade boundaries (ie less marks needed to get better grades) is this true? if so does anyone know what these boundaries are likely to be?
    Usually 10% less,
    50% =c
    60% =b
    70% =a
    that is the usual boundaries for P3.
 
 
 
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