If the columns are labeled a, b, c, d left to right, it appears that we have ...
The value of M is 21.
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Questions like this require that you try different combinations of operations on the numbers shown to see if you can find a relationship. Here, the left column is a perfect square, so that is a clue. The difference of the numbers in the middle columns is a factor of the number in the right column -- another clue. It takes a certain amount of creative thought and familiarity with arithmetic facts. There is no "step-by-step" for a problem like this.
Domain means all the x-values include in the graph.
In this case the graph starts including x-values at 0 and all x-values that are greater then 0.
In other words x can be zero or anything larger
Technically you would show this like so:
x ≥ 0
You use the inequality symbol with the bar underneath because you want to show that 0 is included in the domain. It faces away from the zero and towards the x because x can be larger then 0 not smaller.
I guess in this case you wouldn't be including 0 so your answer is: