If 2x+3y=12 and xy=6 then find 8x^3 + 27y^3
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8x³ + 27y³ = (2x)³ + (3y)³.
Now a³ + b³ = (a + b)(a² + b² - ab)
(2x + 3y)² = 4x² + 9y² + 12ab.
Or 4x² + 9y² = 144 - 72 = 72
Now substitute the values. You will get 12 x 66 = 792
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