Answer:
Approximate length of AB is 9.2 units.
Explanation:
You can use Pythagorean Theorem (check out the picture below) or directly use the distance formula.
Pythagorean Theorem

Hypotenuse is AB and you can read the length of the legs from the graph.

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Another way to do it is to use the distance formula.
The Distance Formula

You can read the points from the graph:
A(-2,-3)
B(4,4)

You can see that both ways give the same answer. Use whatever you prefer.