How do you expand $(y+x)^4$ ?

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Answer 1 · 2018-06-20T18:47:35

$x^4+4x^3y+6x^2y^2+4xy^3+y^4$

since $(x+y)^2=x^2+2xy+y^2$
we can write

$(x^2+2xy+y^2)(x^2+2xy+y^2)=x^4+x^2y^2+2x^3y+x^2y^2+y^4+2xy^3+2x^3y+2xy^3+4x^2y^2$
This is the same like above!

How do you expand (y+x)^4(y+x)^4?