46. 已知函数f(x)=4x4−6tx3+(2t+6)x2−3tx+1(x>0)f(x)=4x^{4}-6tx^{3}+(2t+6)x^{2}-3tx+1(x>0)f(x)=4x4−6tx3+(2t+6)x2−3tx+1(x>0)，若f(x)f(x)f(x)的最小值为0，则t=(t=(t=( )))