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# Abstract Simultaneous Equations watch

1. Hi guys,

Would anyone of you know how to solve:

xy=2
y=x+1

and...

xy=-4
2y=x+6

Thanks
2. Substitute one into another ie:

3. ok so far I have:

x(x+1)
x^2+x=2

What is the next stage?
5. That's a quadratic equation... you learn to do them at the age of 12.
6. (Original post by Sophie Maywood)
xy=2
y=x+1
Sub (y=x+1) into the first equation i.e.

x (x + 1) = 2
x^2 + x = 2
X^2 + x - 2 = 0 (then solve as a quadratic)

(Original post by Sophie Maywood)
and...

xy=-4
2y=x+6
xy = -4
therefore 2xy = -8 (2yx = -8)

sub in the second equation i.e.

x(x + 6) = -8
x^2 + 6x = -8
x^2 + 6x + 8 = 0 (and solve as a quadratic)

7. Ok but on the second equation, how did you obtain the -8
8. (Original post by Sophie Maywood)
Ok but on the second equation, how did you obtain the -8
xy = -4

multiply both sides by 2

2 x (xy) = 2xy

2 x -4 = -8
9. i just looked at your profile (OP) and i cannot believe that you wouldnt know how to do this

your not a troll by any chance are you?
10. no- this is the only part of maths where I get stuck- anyway what's a troll?
11. (Original post by Sophie Maywood)
no- this is the only part of maths where I get stuck- anyway what's a troll?
yeah but this is unbelievably easy (as in the only thing easier than this is just addition and multiplication - and subtraction and division lol)

a troll is generally someone who posts really gay stuff/starts pointless threads just with the intent of annoying people (which im sure youre not )
12. (Original post by Sophie Maywood)
no- this is the only part of maths where I get stuck
You're a further maths student, and cannot solve a simple quadratic equation? That's a bit hard to believe, but whatever
13. (Original post by tomthecool)
You're a further maths student, and cannot solve a simple quadratic equation? That's a bit hard to believe, but whatever
Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

"So what do you do when you meet a door that has PUSH written on it?"

"I try both things. It works out OK half the time."
14. (Original post by Mr M)
Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

"So what do you do when you meet a door that has PUSH written on it?"

"I try both things. It works out OK half the time."
That sounds like a sarcastic joke mate (by your student- not you lol)
15. (Original post by Mr M)
The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

"So what do you do when you meet a door that has PUSH written on it?"

"I try both things. It works out OK half the time."

I admit I often don't understand obvious concepts in mechanics even when it's not technical terminology but the above is just hilarious.
16. (Original post by Mr M)
Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

"So what do you do when you meet a door that has PUSH written on it?"

"I try both things. It works out OK half the time."
Yes, that sounds very believable
That sounds like a sarcastic joke mate (by your student- not you lol)
Sadly not. The rest of the class were already aware of his little "problem".
18. (Original post by Mr M)
Sadly not. The rest of the class were already aware of his little "problem".
maybe they were in on the joke too

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