[tex]b) { - 18x}^{4} {y}^{5} - {24x}^{5} {y}^{4} = {6x}^{4} {y}^{4}( \frac{ {18x}^{4} {y}^{5} }{ {6x}^{4} {y}^{4} } + \frac{ {24x}^{5} {y}^{4} }{ {6x}^{4} {y}^{4} }) = { - 6x}^{4} {y}^{4}(3y + 4x) [/tex]
[tex]c) - 2xy + {3x}^{3}y = xy( \frac{2xy}{xy} + \frac{ { - 3x}^{3}y }{xy}) = - xy(2 - {3x}^{2}) [/tex]
[tex]d) {16xy}^{4} + 24y = 8y( \frac{ {16xy}^{4} }{8y} + \frac{24y}{8y}) = 8y( {2xy}^{3} + 3) [/tex]
