1/(x-2)(x+2)-1/(x-2)-1/(x+2)=(1-(x+2)-(x-2))/(x-2)(x+2)=
1-x-2-x+2/x^2-4=
1-2x/x^2-4
6a^2-10a-a^2-7a-3a-21=5a^2-20a-21
1) 108 * 6^6 ( 6-1)/6^9 - 6^8 = 108 * 6^6 * 5/6^8*(6-1)=108 * 6^6/6^8=108/6^2=108/36=3
2) 3^13(3^2+1)*2^9/3^12(3^2+1)*2^10= 3 *10 * 2^9/10 * 2^10=3/2=1.5
1) (х-4)(х+3)
2) (х-4)(х+1)
3)(х-3)(х+2)
4)(х+5)(х-3)