依题意有:向量a=向量PM,而向量PM=(-t^2+t+5,t^2+t-2)
所以:-t^2+t+5=3,即:t^2-t-2=0-------(1)
t^2+t-2=4,即:t^2+t-6=0-------(2)
解(1)得:t=-1或t=2
解(2)得:t=2或t=-3
所以:t=2
依题意有:向量a=向量PM,而向量PM=(-t^2+t+5,t^2+t-2)
所以:-t^2+t+5=3,即:t^2-t-2=0-------(1)
t^2+t-2=4,即:t^2+t-6=0-------(2)
解(1)得:t=-1或t=2
解(2)得:t=2或t=-3
所以:t=2