determinant: 
(a) 
D<0 means there are no real roots. there are two complex roots with imaginary components.
(b) D=16+20=36>0
D>0 means there are two real roots
(c) D = 20^2-4*4*25 = 0
D=0 means there is one real root with multiplicity 2
Answer:
(2*5) 3*7-1*6÷3*2+1*4÷2*5=216
Answer:
4 divided into 4000 is 1000 with no remainders
4/4000=1000