Hint: Group the 1st, 2nd, and 4th term :).
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Since absolute value is positive even if what is inside the absolute value brackets is negative, and 2 y − x = − ( x − 2 y ) , we can convert all the ( 2 y − x ) into ( x − 2 y ) . Then, group the 1st, 2nd, and 4th term to form a quadratic and the 3rd and 5th term to form a difference of squares . Let a = ∣ x − 2 y ∣ 3 to make the math easier. The quadratic can be factored into ( 7 a − 1 0 9 ) ( a + 2 7 ) and the difference of squares into ( a + 4 5 ) ( a + 2 7 ) . An ( a + 2 7 ) can be factored out, leaving ( a + 2 7 ) ( 8 a − 6 4 ) . Since a represents a cube, ∣ x − 2 y ∣ 3 can be substituted back into the equation. Next, the Cube Sum and Difference formulas can be applied to get a product of two binomials and two trinomials. The Zero-Product Property can be applied here. Since absolute value cannot be negative, this eliminates one of the binomials. Also, the two trinomials have no solutions, which leaves us with ( ∣ x − 2 y ∣ ) = 2 . This can be split into x − 2 y = 2 and x − 2 y = − 2 , and by adding 2 y , subtracting 2 for the 1st equation and − 2 for the second equation, and dividing both sides by 2 y , we can obtain that a = 2 . As a result, a = 2 is the final answer.