Then the equations of BC line and BD line are y=-x+4 respectively.

y=-4x+4

Let p(x 1, 0) and Q(x2, -x2+4).

-4[(x 1+x2)/2]+4 =[0+(-x2+4)]/2

[0-(-x2+4)]/(x 1-x2)= 1/4

x 1 =-28/ 17； x2=60/ 17

t =-28/ 17-(-3)= 23/ 17

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