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Solve for x and y if 4xy=-15 and 4x^3+4y^3=49
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4xy = -15 (1)
4x^3 + 4y^3 = 49 (2)
HINT. Use this trick: Raise both sides of the eq(1) to degree 3. You will get
64x^3*y^3 = -3375, (3)
4x^3 + 4y^3 = 49. (4)
Introduce new variables u = x^3, v = y^3. Then the system (3),(4) takes the form
64uv = -3375,
4u + 4v = 49.
In this way you reduced your quite complicated system to much more simple.
The rest is just a standard exercise in solving quadratic equation.
