1, A (- 1, -2), B (2 2,3), C (-2,-1), then the AC midpoint is the BD midpoint, then: D (-5, -6).

Diagonal line of parallelogram under radical sign = BD = 2

2, vector AB = (3 3,5), vector OC = (-2,-1), then:

(AB-tOC)*OC=0

AB*OC-tOC*OC=0

[3×(-2)+5×(- 1)]-[(-2)? +(- 1)? ]t=0

t=- 1 1/5