Vectors and satisfy and the angle between them is obtuse

MATHEMATICS · Subjective · AP · AP Precalculus · Functions with Parameters, Vectors, and Matrices · Functions with Parameters, Vectors, and Matrices

Problem

Vectors

\mathbf{r}=(t,2,2)

and

\mathbf{s}=(1,t,-3)

satisfy

|\mathbf{r}|=3\sqrt{2}

and the angle between them is obtuse. Find all real values of

t

that meet both conditions.