I assume you mean one that is not rational, such as √2. In such a case, you make a reasonable estimate of it's position, and then label the point that you plot.
For example, you know that √2 is greater than 1 and less than 2, so put the point at about 1½ (actual value is about 1.4142).
For √3, you know the answer is still less than 4, but greater than √2. If both of those points are required to be plotted just make sure you put it in proper relation, otherwise about 1¾ is plenty good (actual value is about 1.7321).
If you are going to get into larger numbers, it's not a bad idea to just learn a few roots. Certainly 2, 3, and 5 (2.2361) and 10 (3.1623) shouldn't be too hard.
Then for a number like 20, which you can quickly workout is √4•√5 or 2√5, you could easily guess about 4½ (4.4721).
They're usually not really interested in your graphing skills on this sort of exercise. They just want you to demonstrate that you have a grasp of the magnitude of irrational numbers.
Answer:
Here we will use the relationships:
And a number:
is between 0 and 1 if a is positive and larger than 1, and n is negative.
if a is positive and 0 < a < 1, then we need to have n positive such that:
0 < a^n < 1
A) 
This is between zero and 1,
B) 
This is greater than 1, because the exponent is positive.
C) 
Because a is smaller than 1, and the exponent is positive, then the expression is between 0 and 1.
D) 
The exponent is negative (and pair) then the expression is between 0 and 1.
Remember that when the exponent is pair, we always have that:
(-N)^m = (N)^m
So (-7)^-2 = 7^-2
In a equation you would look at the slope which would be multiplied by x
In a graph you would do rise over run
For a table you would do burpees which would give you slope or rate of change
Actually, d here represents distance and r 1 and r2 are different rates of travelling d/r gives the time and we know, distance upon time is Rate .
