Find the value of 8x 3 + 27y 3 if 2x +3y =8 and xy = 5.
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Step-by-step explanation:
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Given,
2x+3y=8
xy=5
To find:
8x³+27y³
Solution:
8x³+27y³=(2x)³+(3y)³
we know that,
(a+b)³=a³+b³+3ab(a+b)
a=2x
b=3y
(2x+3y)³=(2x)³+(3y)³+3(2x)(3y)(2x+3y)
(8)³=8x³+27y³+18xy(2x+3y)
512=8x³+3y³+18(5)(8)
512=8x³+3y³+720
512-720=8x³+3y³
(-208)=8x³+3y³
8x³+3y³=(-208)
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