2. Polynomials
hard

यदि $x+y+z=0$ हो, तो दिखाइए कि $x^{3}+y^{3}+z^{3}=3 x y z$ है।

Option A
Option B
Option C
Option D

Solution

Since $x+y+z=0 $                      $\therefore x+y=-z$

or  $(x+y)^{3}=(-z)^{3}$             or $x^{3}+y^{3}+3 x y(x+y)=-z^{3}$

or  $x^{3}+y^{3}+3 x y(-z)=-z^{3}$      $[\because x+y=(-z)]$

or  $x^{3}+y^{3}-3 x y z=-z^{3}$    or $\left(x^{3}+y^{3}+z^{3}\right)-3 x y z=0$

or  $\left(x^{3}+y^{3}+z^{3}\right)=3 x y z$

Hence,            if $x+y+z=0,$ then $\left(x^{3}+y^{3}+z^{3}\right)=3 x y z$

Standard 9
Mathematics

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