Question

先化简,再求值[(a^3+2a^2+4a)/(a^3-8)-10/(a^2+a-6)]/[1-21/(a^2-4)]*(

Answer 1

原式=[a(a^2+2a+4)/(a-2)(a^2+2a+4)-10/(a+3)(a-2)]/[(a^2-25)/(a^2-4)*(a+3)/(a-2)]

=[a/(a-2)-10/(a+3)(a-2)]/[(a+5)(a-5)(a+3)/(a+2)]

=[(a^2+3a-10)/(a-2)]/[(a+2)/(a+5)(a-5)(a+3)]

=[(a+5)(a-2)/(a-2)]/[(a+2)/(a+5)(a-5)(a+3)]

=(a+2)/(a^2-2a-15)