Answer
$x^{4}-1$
Work Step by Step
$18x^{4}+2x^{3}y^{3}-1-2y^{3}x^{3}-17x^{4}$
Rewrite this expression by putting the $x$ of the fourth term right after the coefficient:
$18x^{4}+2x^{3}y^{3}-1-2x^{3}y^{3}-17x^{4}=...$
Simplify the expression by combining like terms:
$...=(18-17)x^{4}+(2-2)x^{3}y^{3}-1=...$
$...=x^{4}+(0)x^{3}y^{3}-1=...$
$...=x^{4}-1$
