A/b(a-1):a/(a-1)(a+1)=a/b(a-1)*(a-1)(a+1)/a=(a+1)/b
-25Q/b²c^5:(-15Q²)/b^5c³=(25Q*b^5c³)/(15Q*b²c^5)=5b³/3b²Q
(x²+x-6)/(x²+6x+9)=(x+3)(x-2)/(x+3)²=(x-2)/(x+3)
x²+x-6=0
x1+x2=-1 U x1*x2=-6⇒x1=-3 U x2=2
(a²-14ab+49b²)/(49b²-7ab)=(7b-a)²/7b(7b-a)=(7b-a)/7b