А)=7х^2-35х+х-5+6х^2+21х-4х-14=13х^2-17х-19
б)=10а^2-2ах+15ах-3х^2-10а^2+3ах-10ах+3х^2=6ах
(x²-4)/(x²(x+3)-4(x+3))=0
(x²-4)/(x²-4)(x+3)=0
ОДЗ: x≠2, x≠-2, x≠-3
1/(x+3)≠0
x∈∅
(x²-3x-10)/(x-5)=0
ОДЗ: x≠5
(x²-5x+2x-10)/(x-5)=0
(x-5)(x+2)/(x-5)=0
x+2=0
x= -2