4. Let $v_1 = \begin{bmatrix} 1 \\ 2 \end{bmatrix}$ and $v_2 = \begin{bmatrix} -3 \\ 4 \end{bmatrix}$.
(a) Describe the span of $v_1$ and $v_2$ in $\mathbb{R}^2$. What geometric shape does it represent?
(b) Determine if the vector $b = \begin{bmatrix} 4 \\ 1 \end{bmatrix}$ is in the span of $v_1$ and $v_2$.
(c) If b is in the span, find the linear combination of $v_1$ and $v_2$ that equals b.
