The GCF is 7c.
There is a formula for the "difference of squares." In this case, the answer is (5b - 14c)(5b + 14c)
It is: 14c-5c = 9c
The most common element used is the element Carbon. More precisely, Carbon 14 or simply 14C, an isotope of Carbon (same number of protons but two more neutrons than plain old 12C, the most common variety of carbon) is used. All living organism have 14C and the amount of 14C in a living organism is constant throughout it's life. However, as the creature dies, the 14C level drops. The rate of drop is know precisely. Therefore, by measuring how much 14C is in the remains, the time the organism died can be known (usually to within decades).
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Common Isotopes of Carbon are 12C (6 neutrons), 13C (7 neutrons), and 14C (8 neutrons).
The isotope 14C has in the nucleus 6 protons and 8 neutrons. The electron configuration is [He]2s22p2.
14 atoms of carbon.
14c + c + 12 = 15c + 12 = 3(5c + 4)
2 x 2 x 7 x 7 x c x c
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14 atoms of carbon.
It is an expession that can be simplified to: 6c