Question

2a+6分之a+15-a^2+6a+9分之a^2-81除以a+3分之a-9

Answer 1

原式=[(a+15)/(2a+6)]-[(a²-81)/(a²+6a+9)]÷[(a-9)/(a+3)]

=[(a+15)/(2a+6)]-[(a+9)(a-9)/(a+3)²]×[(a+3)/(a-9)]

=[(a+15)/(2a+6)]-[(a+9)/(a+3)]

={ (a+15)/[2(a+3)] }-{ 2(a+9)/[2(a+3)] }

=[(a+15)-2(a+9)]/[2(a+3)]

=(a+15-2a-18)/[2(a+3)]

=(-a-3)/[2(a+3)]

=-(a+3)/[2(a+3)]

=-1/2