Answer:
See explanation
Step-by-step explanation:
1. R is the set of all integers with absolute value less than 10, thus
![R=\{a\in \mathbb{Z}\ :\ |a|](https://tex.z-dn.net/?f=R%3D%5C%7Ba%5Cin%20%5Cmathbb%7BZ%7D%5C%20%3A%5C%20%7Ca%7C%3C10%20%5C%7D%3D%5C%5C%20%5C%5C%3D%5C%7B-9%2C%5C%20-8%2C%5C%20-7%2C%5C%20-6%2C%5C%20-5%2C%5C%20-4%2C%5C%20-3%2C%5C%20-2%2C%5C%20-1%2C%5C%200%2C%5C%201%2C%5C%202%2C%5C%203%2C%5C%204%2C%5C%205%2C%5C%206%2C%5C%207%2C%5C%208%2C%5C%209%5C%7D)
2. A is its subset containing all natural numbers less than 10, thus
![A\subset R\\ \\A=\{b\in \mathbb{N}\ :\ b](https://tex.z-dn.net/?f=A%5Csubset%20R%5C%5C%20%5C%5CA%3D%5C%7Bb%5Cin%20%5Cmathbb%7BN%7D%5C%20%3A%5C%20b%3C10%5C%7D%3D%5C%7B1%2C%5C%202%2C%5C%203%2C%5C%204%2C%5C%205%2C%5C%206%2C%5C%207%2C%5C%208%2C%5C%209%5C%7D)
3. B is the set of all integer solutions of inequality 2x+5<9 that are less than 10 by absolute value (and therefore, it is also a subset of R). First, solve the inequality:
![2x+5](https://tex.z-dn.net/?f=2x%2B5%3C9%5C%5C%20%5C%5C2x%3C9-5%5C%5C%20%5C%5C2x%3C4%5C%5C%20%5C%5Cx%3C2)
Thus,
![B\subset R\\ \\B=\{c\in \mathbb{Z}\ :\ 2c+5](https://tex.z-dn.net/?f=B%5Csubset%20R%5C%5C%20%5C%5CB%3D%5C%7Bc%5Cin%20%5Cmathbb%7BZ%7D%5C%20%3A%5C%202c%2B5%3C9%2C%5C%20%7Cc%7C%3C10%5C%7D%3D%5C%7Bc%5Cin%20%5Cmathbb%7BZ%7D%5C%20%3A%5C%20c%3C2%2C%5C%20%7Cc%7C%3C10%5C%7D%3D%5C%5C%20%5C%5C%3D%5C%7B-9%2C%5C%20-8%2C%5C%20-7%2C%5C%20-6%2C%5C%20-5%2C%5C%20-4%2C%5C%20-3%2C%5C%20-2%2C%5C%20-1%2C%5C%200%2C%5C%201%5C%7D)
See the diagram in attached diagram.
Note that
![A\cup B=R\\ \\A\cap B=\{1\}.](https://tex.z-dn.net/?f=A%5Ccup%20B%3DR%5C%5C%20%5C%5CA%5Ccap%20B%3D%5C%7B1%5C%7D.)
A. the colonists must work together in order to be strong.
Begin by factoring 2 out of 2x^2 - 2x - 12 equals 0:
2(x^2 - x - 6) = 0
2(x - 3)(x + 2) = 0. 2 is never zero, but x-3 and x+2 can each be set = to 0:
This results in x = 3 and x = -2. The equation is true for these two x-values.