if 2x+3y=8 and xy=2,find value of 8x^3+27y^3
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Answer:
476 is the answer.
Step-by-step explanation:
8x³+27y³
=(2x)³+(3y)³
=(2x+3y){(2x)²-2x×3y+(3y)²}
=(2x+3y)(4x²-6xy+9y²)
=(2x+3y){(2x)²+(3y)²}-6xy
=(2x+3y){(2x+3y)²-2×2x.3y}-6xy
=(2x+3y)(2x+3y)²-12xy-6xy
=(2x+3y)(2x+3y)²-18xy
=8×8²-18×2
=8×64-36
=512-36
=476
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