#hey! someone answered this question but i still don't get how they got it

16 messages · Page 1 of 1 (latest)

fringe orchid
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can someone explain?

orchid tundra
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which is 36

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so 3x + 2y = 36

fringe orchid
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ohhh ok so then how did this person get x = 4?

orchid tundra
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well we know that y is bigger than x so at this point I’d probably just do trial and error

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but there’s probably a better way so im not sure

tawdry raven
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I actually didn’t find the two pairs but you could just find the point of intersection of the lines and sub values of x that are greater than the x value you find for the point of intersection

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thats cold by me 36 / 2 is 18 not 36 💀

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if you do x = -1.5x + 18, youd get x = 7.2 so if you subtitute any integer x thats greater than 7.2 into the equation y = -1.5x + 18, you should get a pair of x and y that should satisfy the equation in the question

silk goblet
# fringe orchid can someone explain?

This is what is known as a "Diophantine equation" (where you have more variables than equations and are looking for only integer / positive integer solutions)

This one is fairly basic and i'll show u a technique to solve this one

We have 36 = 3x+2y

The main idea is kind of a very systematic trial and error

First observe that 36 is dividible by 2 so 3x+2y is divisible by 2 so x is divisible by 2 (since 2y is always even) (Side note: you can use this same logic to deduce that y is divisible by 3)

Since x<y we can start checking from the smallest value of x (which is divisible by 2)

If x=2 then 36=6+2y so y=15
If x=4 then 36=12+2y so y=12
If x=6 then 36=18+2y so y=9

If x=8 then 36=24+2y so y=6 but this is impossible since now x>y

Hence the possible solutions are (2,15) (4,12) and (6,9)

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If this comes up on a gcse paper then you definitely don't have to go into all this detail and since the question just wants 2 sets of values for (x,y) the best thing u can do is trial and error

silk goblet