1.

यदि `x+y=7` है तो `x^(3)+y^(3)+21xy` का मान क्या होगा?A. 243B. 143C. 343D. 443

Answer» Correct Answer - C
`x+y=7` (cubing both sides)
`(x+y)^(3)=(7)^(3)`
`x^(3)+y^(3)=3(x+y)xy=343`
`x^(3)+y^(3)+21xy=343`
` x^(3)+y^(3)+21xy=343`


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