A²-a-30=0
D=1-4*(-30)=121
a= 1+11/2=12/2=6
a=1-11/2= -10/2= -5
a²-a-30=(a-6)(a+5)
2a²-15a-50=0
D=225-4*2*(-50)=625
a= 15+25/4=10
a= 15-25/4= -10/4=-2,5
2a²-15a-50= 2(a+2,5)(a-10)=(2a+5)(a-10)
(a-6)(a+5)/(0,5a-3)=2(0,5a-3)(a+5)/(0,5a-3)=
=2(a+5)=2a+10
(2a+5)(a-10)/(2a+5)= a-10
2a+10+a-10=3a