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kaulnikhil
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If x and y are non-zero integers and |x| + |y| = 32, what is xy?
(1) -4x - 12y = 0
(2) |x| - |y| = 16
[spoiler]i took each combination of x and y
x+y = 32
-x -y = 32
x-y =32
-x+ y =32
only one of them satisfies the equation so ans is A
is there any way other way to solve this [/spoiler].
the orginal solution is as follows ..
(1) SUFFICIENT: Statement (1) can be rephrased as follows:
-4x - 12y = 0
-4x = 12y
x = -3y
If x and y are non-zero integers, we can deduce that they must have opposite signs: one positive, and the other negative. Therefore, this last equation could be rephrased as
|x| = 3|y| how can we say this ?????
doesnt this mean 1 x...=3y
2...x = -3y
3...-x =3y
4.. - x = -3y
how can we put x = -3y as |x| = 3|y|???
we cant be sure about the other three
We don't know whether x or y is negative, but we do know that they have the opposite signs. Converting both variables to absolute value cancels the negative sign in the expression x = -3y.
We are left with two equations and two unknowns, where the unknowns are |x| and |y|:
|x| + |y| = 32
|x| - 3|y| = 0
Subtracting the second equation from the first yields
4|y| = 32
|y| = 8
Substituting 8 for |y| in the original equation, we can easily determine that |x| = 24. Because we know that one of either x or y is negative and the other positive, xy must be the negative product of |x| and |y|, or -8(24) = -192.
(1) -4x - 12y = 0
(2) |x| - |y| = 16
[spoiler]i took each combination of x and y
x+y = 32
-x -y = 32
x-y =32
-x+ y =32
only one of them satisfies the equation so ans is A
is there any way other way to solve this [/spoiler].
the orginal solution is as follows ..
(1) SUFFICIENT: Statement (1) can be rephrased as follows:
-4x - 12y = 0
-4x = 12y
x = -3y
If x and y are non-zero integers, we can deduce that they must have opposite signs: one positive, and the other negative. Therefore, this last equation could be rephrased as
|x| = 3|y| how can we say this ?????
doesnt this mean 1 x...=3y
2...x = -3y
3...-x =3y
4.. - x = -3y
how can we put x = -3y as |x| = 3|y|???
we cant be sure about the other three
We don't know whether x or y is negative, but we do know that they have the opposite signs. Converting both variables to absolute value cancels the negative sign in the expression x = -3y.
We are left with two equations and two unknowns, where the unknowns are |x| and |y|:
|x| + |y| = 32
|x| - 3|y| = 0
Subtracting the second equation from the first yields
4|y| = 32
|y| = 8
Substituting 8 for |y| in the original equation, we can easily determine that |x| = 24. Because we know that one of either x or y is negative and the other positive, xy must be the negative product of |x| and |y|, or -8(24) = -192.
