Question

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

Answer 1

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

Explanation:

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!