How can I describe the union between this specific set and the Fibonacci sequence set?

Question

I have two sets, $M_1$ and $M_2$:

$$ M_1 = \{x\mid x \text{ is a Fibonacci number}\}\\ M_2 = \{x \mid −10 \leq x \leq 10\} $$ How can I describe the union between these sets?

$$M_1 \cup M_2$$

Thanks.

Answer 1

If $A,B$ are sets, then $A \cup B$ is the set of all elements of $A$ or $B$. In other words, $M_1 \cup M_2$ is the set of all Fibonacci numbers together with integers in $[-10,10]$.