A6.
(4a^2-12ab+9b^2)/(15b-10a)=(2a-3b)^2/5(3b-2a)=(3b-2a)^2/5(3b-2a)=(3b-2a)/5=0,6b-0,4a
A7.
mn+mt+2n+2t=m(n+t)+2(n+t)=(m+2)(n+t)
A8.
(2p^2-8)/(2p-p^2)=2(p-2)(p+2)/p(2-p)=(-2p-4)/p
A9.
25y^2-20yz+4z^2=(5y-2z)^2
A10.
-c^8+5c^7+c-5=-c^7(c-5)+(c-5)=(1-c^7)(c-5)=(c^7-1)(5-c)