a) 5x^2(x - y) - 15xy(y - x); b) x^6 - 1; c) 3x^2 + 5x - 3y^2 - 5y

a) 5x2x−y−15xyy−x

=5x2x−y+15xyx−y

=x−y5x2+15xy

=5xx−yx+3y.

b) x6−1

=x32−12

=x3−1x3+1

=x−1x2+x+1x+1x2−x+1.

c) 3x2+5x−3y2−5y

=3x2−3y2+5x−5y

=3x2−y2+5x−y

=3x−yx+y+5x−y

=x−y3x+3y+5