Just use the distance between two points formula.
It will be found in your text or your notes.
Find the distance between the two points: P1= ( -1,0) and P2= (2,4)
2 answers
Distance = Square Root ((x2-x1)^2 +(y2-y1)^2)
Square Root ((2-(-1))^2 + (4-0)^2)
Square Root ((2+1)^2 + (4)^2
Square Root ((3)^2 + 16)
Square Root (9+16)
Square Root (25)
= 5
Square Root ((2-(-1))^2 + (4-0)^2)
Square Root ((2+1)^2 + (4)^2
Square Root ((3)^2 + 16)
Square Root (9+16)
Square Root (25)
= 5