Please hlep me ! (Maths)

You can not add up the the coordinations (坐標), it is meaningless.
You can ask the distance between two points, or equation of lines (straight or curve) passing through these points.
1) distance between them is
√[(1-2)2 + (1-2) 2]= √2 = 1.414
The equation passing through : y=mx + c
y=2, x=2, 2=2m+c
y=1, x=1, 1=m+c, then c=0, m=1, y=x

2) distance between them is
√[(3-1)2 + (2-0) 2]= √8 = 2.828
The equation passing through : y=mx + c
y=2, x=3, 2=3m+c
y=0, x=1, 0=m+c, then c=-1, m=1, y=x-1