158.
1) b²-15b+14=b²-14b-b+14=b*(b-14)-(b-14)=(b-14)*(b-1).
2) -x²-6x+7=-(x²+6x-7)=-(x²+6x+x-x-7)=-(x²+7x-x-7)=-(x*(x+7)-(x+7))=
=-(x+7)*(x-1)=(x+7)*(1-x).
3) 30y²-10y-100=10*(3y²-y-10)=10*(3y²-y-5y+5y-10)=10*(3y²-6y+5y-10)=
=10*(3y*(y-2)+5*(y-2))=10*(y-2)*(3y+5).
159.
1) (x²-8x+7)/(x-7)=(x²-7x-x+7)/(x-7)=x*(x-7)-(x-7)/(x-7)=(x-7)*(x-1)/(x-7)=x-1.
2) (4x-8)/(x²-3x+2)=4*(x-2)/(x²-2x-x+2)=4*(x-2)/(x*(x-2)-(x-2))=
=4*(x-2)/((x-2)*(x-1))=4/(x-1).
3) (4x²+x-5)/(16x²-25)=(4x²-4x+4x+x-5)/((4x-5)*(4x+5))=
=(4x²-4x+5x-5)/((4x-5)*(4x+5)=4x*(x-1)+5*(x-1)/((4x-5)*(4x+5))=
=(x-1)*(4x+5)/((4x-5)*(4x+5))=(x-1)/(4x-5).