Answer
A line through $\begin{bmatrix}8\\2\\-6\end{bmatrix}$
Work Step by Step
Since $v_2=1.5v_1$, the span of $\{v_1, v_2\}$ is merely the set of vectors that are scalar multiples of $v_1$.
This can be clearly shown, for any vector $v_3$ in the span of $\{v_1, v_2\}$, where $a$, $b$, and $c$ are real numbers:
$$v_3 = av_1 + bv_2 = av_1 + 1.5bv_1 = (a+1.5b)v_1 = cv_1$$
