find the value of x³ +y³+15xy-123 if x+y= 5.
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Answered by
21
x³+y³+15xy-123
⇒(x+y)³=x³+y³+3xy(x+y)
⇒5³=x³+y³+3xy(5),substituting x+y=5
⇒125=x³+y³+15xy
Substituting the above equation in the gn. equation,
⇒5-123
⇒-118
I believe the answer would be the answer would be useful, if you feel so please choose it the best one.
By
MASelvam
Booksworm
⇒(x+y)³=x³+y³+3xy(x+y)
⇒5³=x³+y³+3xy(5),substituting x+y=5
⇒125=x³+y³+15xy
Substituting the above equation in the gn. equation,
⇒5-123
⇒-118
I believe the answer would be the answer would be useful, if you feel so please choose it the best one.
By
MASelvam
Booksworm
Answered by
11
x^3[tex]x+y=5(cubing both sides) \\
(x+y)^3= 125 \\
x^3+y^3+3x^2y+3y^2x=125 \\ x^3+y^3+3xy(x+y)= 125
\\ x^3+y^3+(3*5)xy=125(x+y=5 is given) \\
x^3+y^3+15xy=125
\\ substituting the values, we will get
125-123= 2
\\ 2 is the answer[/tex]
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