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    Hi, please could somebody help me with this equation:
    x^2 + y^2 = 136
    4x + y =34
    Whenever I do this equation, I keep getting the answer x=8.5 and y =0 for both sets of solutions but this is wrong.
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    (Original post by Mazza2000)
    Hi, please could somebody help me with this equation:
    x^2 + y^2 = 136
    4x + y =34
    Whenever I do this equation, I keep getting the answer x=8.5 and y =0 for both sets of solutions but this is wrong.
    Haven't done quadratics in a good few years, but I got x=6 y=10

    I worked it out by looking at the botom equation and testing with different values for x:
    I assumed the value was under 10 (4x10 would be over 34 and I didn't think y would be a negative).
    I randomly went for x being 5 to start with... that got to y needing to be 14 to make the 34 and meant that the above equation would equal well over 136 (14^2 being over 100 as it is).
    I knew x had to be higher than 5 so tested 6 next. 4x6 is 24 so y would need to be 10 to make 34. 10x10 is 100 and 6x6 is 36 so both x and y squared add to 136.
    Doubble check both the equations with those values and it's confirmed.

    Usually at GCSE (from my experience) both values will be under 10 and be whole numbers since they will often expect it to be done without a calculator in exams and dealing with decimals in your head is just too mean.

    How did you get to the values you did for x and y?
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    (Original post by Mazza2000)
    Hi, please could somebody help me with this equation:
    x^2 + y^2 = 136
    4x + y =34
    Whenever I do this equation, I keep getting the answer x=8.5 and y =0 for both sets of solutions but this is wrong.
    This is my working out and what answers I got:
    Name:  image.jpg
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    hope this help, I broken it down for you and if you're still stuck message me if it dosent make sense
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    (Original post by Taahira_)
    This is my working out and what answers I got:
    Name:  image.jpg
Views: 117
Size:  517.1 KB
    hope this help, I broken it down for you and if you're still stuck message me if it dosent make sense
    Okay so I got the same answer as you but now I'm confused too. That looks WAY more complicated than anything I did at GCSE.
    I'm veguely familiar with rearanging the equation to make something else the subject but then you lost me with all the square roots and big numbers.
    Could you maybe explain to me too? Whats up with all the a and b and c and everything? :/

    Edit: okay no I think i've got it now. wow it's been way too long since i've done any maths. I used to be good at this!
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    (Original post by Kindred)
    Okay so I got the same answer as you but now I'm confused too. That looks WAY more complicated than anything I did at GCSE.
    I'm veguely familiar with rearanging the equation to make something else the subject but then you lost me with all the square roots and big numbers.
    Could you maybe explain to me too? Whats up with all the a and b and c and everything? :/
    a, b and c are components of the quadratic formula. a = 17 b= -272 c= 1020. You sub in the values.
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    (Original post by SubZero~)
    a, b and c are components of the quadratic formula. a = 17 b= -272 c= 1020. You sub in the values.
    I remember doing that up to the last bit with a, b, c. I have no idea what we were taught instead, but i'm pretty sure we never did anything like that.
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    (Original post by SubZero~)
    a, b and c are components of the quadratic formula. a = 17 b= -272 c= 1020. You sub in the values.
    You dont need to sub in if you dont want to , just divide eveything by 17 to get x^2-16x+60=0
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    (Original post by Ayaz789)
    You dont need to sub in if you dont want to , just divide eveything by 17 to get x^2-16x+60=0
    Pretty sure that takes longer than shoving it into a formula.
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    (Original post by Kindred)
    I remember doing that up to the last bit with a, b, c. I have no idea what we were taught instead, but i'm pretty sure we never did anything like that.
    Weird. Pretty sure most people were taught this at GCSE.
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    (Original post by SubZero~)
    Pretty sure that takes longer than shoving it into a formula.
    Nope , then you put them into 2 brackets (x-6)(x-10) & you've got your 2 x values
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    (Original post by Ayaz789)
    Nope , then you put them into 2 brackets (x-6)(x-10) & you've got your 2 x values
    Okay.
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    Okay so using the proper method of switching equation round etc instead of just guessig a value I can get this far: (im using * as squared cos lazy typing)

    y=34-4x y*=(34-4x)*
    x*+(34-4x)*=136
    x*+(34-4x)(34-4x)=136 ...... putting x first
    x*+(-4x+34)(-4x+34)=136 ...... simplifying brackets with squaring negs making pos
    x*+(16x*+34*)=136
    x*+(16x*+1156)=136 ..... simplifying again
    17x*+1156=136 .... making x the subject
    136-1156=17x*
    I'm lost here. I think I messed up pos and negs somewhere.



    Baby steps from where I am maybe? please? (assuming I haven't messed it up completely)
    I don't know why i'm so invested in this now since i'm never going to have to do this stuff again, but whatever.
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    (Original post by Mazza2000)
    Hi, please could somebody help me with this equation:
    x^2 + y^2 = 136
    4x + y =34
    Whenever I do this equation, I keep getting the answer x=8.5 and y =0 for both sets of solutions but this is wrong.
    Let's do it here then time for latex...

    x^2 +y^2 =136
    4x+y=34

    y=34-4x

    x^2+\left(34-4x\right)^2 =136

    x^2+1156-272x+16x^2=136

    17x^2-272x+1020=

    remember to check and see if you can simplify....(always a good idea too otherwise you'll end up with huge numbers)
    luckily this divides by 17

    x^2-16x+60=0

    \left(x-10\right) \left(x-6\right)

    sub values of x into

    y=34-4x
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    Hi,
    Thanks guys for the reply! Makes sense
 
 
 
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