| If \[x+y=12\] and \[xy=27,\] then \[{{x}^{3}}+{{y}^{3}}\] equal to |
A) 752
B) 754
C) 756
D) 780
Correct Answer: C
Solution :
| \[x+y=12\] and \[xy=27\] |
| \[{{x}^{3}}+{{y}^{3}}={{(x+y)}^{3}}-3xy\,(x+y)\] |
| \[={{(12)}^{3}}-3\times 27\,(12)\] |
| \[=1728-81\times 12\] |
| \[=1728-972=756\] |
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