Question 359427
{{{(x+y)^3=x^3+3x^2y+3xy^2+y^3}}}
.
.
.
{{{(x+y)^3=x^3+y^3}}} when
{{{3x^2y+3xy^2=0}}}
{{{highlight(x=-y)}}}
.
.
.
Example, {{{x=5}}}, {{{y=-5}}}
{{{(x+y)^3=0}}}
{{{x^3+y^3=125-125=0}}}
{{{(x+y)^3=x^3+y^3}}}

.
.
.
Counterexample, {{{x=5}}},{{{y=5}}}
{{{(x+y)^3=10^3=1000}}}
{{{x^3+y^3=125+125=250}}}
{{{(x+y)^3<>x^3+y^3}}}