they are only a couple of inches long
No - two are longer for catching prey
no they have many sizes depending on what kind it is
no, most have 7-9 tentacles
no
The answer is very simple. Jellyfish are cnidarians. Octopi are not. Because the octopus does not have the same head structure as the jellyfish. Also octopi are cephalopods. They are closer to mollusks in the bases of things but the tentacles are different. Just because they have tentacles does not mean they are in the same categories. But octopi and squid are in the same category as mollusks such as snails. That is a different story though. But that is why they are not the same.
an octopus has only 8 tentacles while squids can have 10
Cnidereans have pressure-sensitive poison glands called nematocysts that are usually on their tentacles. When their [prey] touches these nematocysts, small "fangs" inject poison into the [prey]. The poison in the nematocysts can paralyze or even kill small animals. Once the prey is subdued, the tentacles pull the prey towards the mouth.
The answer to, "Segments that have the same length" Is Congruent Segments!
Sides with the same length are congruent.
No! Length squared will be the length times the length again. Length times height is going to find the area so it will not be the same.
They both use there tentacles to capture there prey and the mouth is near the center of the body
not exactly, no. but they are round about the same length
Scalene triangle has no sides of same length