А) 5x^2+9x-2=0,
D=81+4*4*2=81+40=121=11^2,
x1=-9+11/10=1/5,
x2=-9-11/10=-2,
5x^2+9x-2=5(x-1/5)(x+2)=(5x-1)(x+2),
x^2-2x-8=0,
D=1+8=9,
x1=1+3=4,
x2=1-3=-2,
x^2-2x-8=(x+2)(x-4),
(5x^2+9x-2)/(x^2-2x-8)=(5x-1)(x+2)/(x+2)(x-4)=(5x-1)/(x-4).
б) (3x^2+7x-6)=0, D=49+4*3*6=49+72=121=11^2,
x1=-7+11/6=2/3,
x2=-7-11/6=-3,
3x^2+7x-6=3(x-2/3)(x+3)=(3x-2)(x+3),
2y-3xy-15x+10=y(2-3x)+5(2-3x)=(2-3x)(y+5),
x(3x^2+7x-6)/(2y-3xy-15x+10)=x(3x-2)(x+3)/-(3x-2)(y+5)=-(x(x+3))/(y+5).