a^6 (a^-2 - a^-3) (a^2 + a^3)^-1= a^6 (1/a^2 - 1/a^3) 1/(a^2 + a^3)= a^6 (a^3 - a^2) 1/(a^2 + a^3)= a^6 a^2 1/(a^2 + a^3)= a^8 / (a^2 + a^3)= a^8 / a^2(1 + a)= a^6(1 + a)
a^6 (a^-2 - a^-3) (a^2 + a^3)^-1
= a^6 (1/a^2 - 1/a^3) 1/(a^2 + a^3)
= a^6 (a^3 - a^2) 1/(a^2 + a^3)
= a^6 a^2 1/(a^2 + a^3)
= a^8 / (a^2 + a^3)
= a^8 / a^2(1 + a)
= a^6(1 + a)