Answer
$2x^4+3x^3-5x^3+4x^4=6x^4-2x^3$
Work Step by Step
Organise pairs of coefficients such that the coefficients will correspond to $6$ and $2$.
$2x^\square+3x^\square-5x^\square+4x^\square=6x^4-2x^3$
$2+4=6$
$3-5=-2$. So
$2x^4+4x^4=6x^4$
$3x^3-5x^3=-2x^3$
$2x^4+3x^3-5x^3+4x^4=6x^4-2x^3$.
