We have to solve
x+y+2xy=-11
...(1)
2x^2y+2xy^2=-12
...(2)
(2)
=> x^2y +
xy^2 = -6
=> xy(x+y) =
-6
(1)
=> x+ y + 2xy =
-11
If we take the variables x+y and xy together as A and
B, we get
A*B = -6
2A + B =
-11
A( -11 - 2A) =
-6
=> 11A + 2A^2 - 6 =
0
=> 2A^2 + 11A - 6 =
0
=> 2A^2 + 12A - A - 6 =
0
=> 2A ( a + 6) - 1(A + 6) =
0
=> (2A - 1)(A + 6) =
0
=> A = 1/2 and A =
-6
=> B = -12 , 1
B =
x+y = -12
A = xy = 1/2
From
this we get the equation
x^2 + 12x - 1/2 =
0
=> 2x^2 + 24x - 1 =
0
x1 = [-24 + sqrt(576 +
8 )]/4
=> x1 = [-24 + sqrt
584]/4
=> x1 = -6 + sqrt 584 /
4
=> y1 = -6 - sqrt 584 /
4
x2 = -6 - sqrt 584 / 4
y2 =
-6 + sqrt 584 / 4
Now, for the values -6 and 1 we
have:
x^2 - x - 6 = 0
x^2 - 3x
+ 2x - 6 =0
=> x(x - 3) + 2( x - 3)
=0
=> (x + 2)(x - 3)
=0
x1 = -2
y1 =
3
x2 = 3
y2 =
-2
So the solutions for x and y are (-2 ,
3),( 3, 2), (-6 + sqrt 584 / 4, -6 - sqrt 584 / 4), ( -6 - sqrt 584 / 4 , -6 + sqrt 584
/ 4)
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