How Do I Find The Length Of A Segment?

The length of a line segment is basically the distance between one end to the other end of the line segment. The link below gives a detailed account of how to find a line segment length in geometry.
www.regentsprep.org

Use the distance formula...
Square root of (x2-x1) ^2 + (y2-y1) ^2
good luck (:

What is the length of the segment with endpoints (-3,4) and (5,4)?

This is the answer to a problem asking students to find the length of a segment. There is a line over the AB I just can't figure out how to put it their.  Is this the right answer?  AB=7.2

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...... Express the length of this segment using square roots