∴m=2×2=4，

(2) The straight line Y=KX+b passes through (1, 3) and (2,4), and the equation is obtained:

{3=K+b

{4=2K+b

Solution: K= 1, b=2,

Analytical formula of straight line: Y=X+2.

(3) The straight line Y=X+2 intersects the X axis at (-2,0),

sδ= 1/2×2×4 = 4 .