Answer:
2.80
Explanation:
Seeing that your scale is 1cm to 1unit to on both axes
If you add a point C then draw lines connecting them it should look like the diagram above
But the distance between A to C and B to C are both 2 cm
Giving you a right angled triangle
So using the Pythagoras theorem
AB²=AC²+BC²
AB²=2²+2²
AB²=4+4
AB²=8
Take square root of both sides
√AB²=√8
AB= 2.828
To the nearest tenth that will be
AB=2.80