Find the value of of x^3+y^3+15xy-125 if x+y=5
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Answered by
3
it will be 0 how
x^3+y^3 +15xy -125
(using X^3+y^3 = (x+y)(x^2-xy+y^2) )
(x+y)(x^2-xy+y^2)+ 15xy -125
since x+y = 5
5(x^2-xy+y^2)+ 15 xy -125
5 x^2 - 5xy +5y^2 +15xy -125
5x^2 + 10 xy + 5y^2 -125
5(X^2 + 2xy + y^2)-125
5(x+y)^2 -125
5(5)^2 -125
5(25) -125
125 -125
=0
x^3+y^3 +15xy -125
(using X^3+y^3 = (x+y)(x^2-xy+y^2) )
(x+y)(x^2-xy+y^2)+ 15xy -125
since x+y = 5
5(x^2-xy+y^2)+ 15 xy -125
5 x^2 - 5xy +5y^2 +15xy -125
5x^2 + 10 xy + 5y^2 -125
5(X^2 + 2xy + y^2)-125
5(x+y)^2 -125
5(5)^2 -125
5(25) -125
125 -125
=0
Answered by
1
0
Use arbitrary value Eg 1,4 and 5,0
Plug it in the equation, you'll end up with 0.
Use arbitrary value Eg 1,4 and 5,0
Plug it in the equation, you'll end up with 0.
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