(X^3YX^2-20XY+21X^3)+(15X^3YZ^2-3XY)
Adding these two expressions together, we can combine like terms:
(X^3YX^2-20XY+21X^3)+(15X^3YZ^2-3XY)
Grouping terms with similar powers of X and combining coefficients:
(X^3YX^2 + 21X^3) + (15X^3YZ^2 - 20XY - 3XY)
Factoring out common factors:
X^3(YX^2 + 21) + XY(15X^2Z^2 - 20 - 3)
Simplifying further:
X^3YX^2 + 21X^3 + 15X^3YZ^2 - 20XY - 3XY
X^5Y + 21X^3 + 15X^3YZ^2 - 23XY