a=(3,4),b=(-4,3)
所以a^2=25,b^2=25,a·b=0
(1)
若m垂直于n,则m·n=0
即[ka+(2t-1)b][a+(t-1)b]=ka^2+(2t-1)(t-1)b^2=25k+25(2t-1)(t-1)=0
所以k=-(2t-1)(t-1)
因为-4≤t≤3
所以
-9≤2t-1≤5
-5≤t-1≤2
-25≤(2t-1)(t-1)≤10
-10≤-(2t-1)(t-1)≤25
即：-10≤k≤25
(2)
m=ka+(2t-1)b=(3k-8t+4,4k+6t-3)
n=a+(t-1)b=(-4t+7,3t+1)
若m//n
则(3k-8t+4)/(4k+6t-3)=(-4t+7)/(3t+1)
化简得k=(2t-1)/(t-1),t∈[-4,1)∪(1,3]