We will use the Descartes` rule of signs and see how many times the signs change from positive to negative and from negative to positive from one term to the next ( two consecutive terms are with different signs ).
In this case it is 4 times ( +7x13 to -12x9, -12x9 to +16x5, +6x5 to -23 x and finally -23x to +42 ).
Answer: There are 4 real zeroes.
Here is the order:
Gene,
DNA,
Chromosome,
Nucleus,
Cell,
Organism.
[Hey if this is wrong, don't post a rude reply! Message me and I will try to correct the answer!]
Answer:
There are 7800 meters in 7.8 km
