Write each vector as a linear combination of the vectors in S. (If not possible, enter IMPOSSIBLE.)
S = {(6, -7, 8, 6), (4, 6, -4, 1)}
(a) u = (2, 19, -16, -4)
u = \begin{pmatrix} -1 \\ \\ \end{pmatrix} s_1 + \begin{pmatrix} 3 \\ \\ \end{pmatrix} s_2
(b) v = \begin{pmatrix} \frac{57}{2}, \frac{123}{4}, -18, \frac{21}{2} \end{pmatrix}
v = \begin{pmatrix} \frac{3}{2} \\ \\ \end{pmatrix} s_1 + \begin{pmatrix} \frac{9}{4} \\ \\ \end{pmatrix} s_2
(c) w = (-4, -14, \frac{21}{8}, \frac{59}{8})
w = \begin{pmatrix} -1 \\ \\ \end{pmatrix} s_1 + \begin{pmatrix} \frac{1}{8} \\ \\ \end{pmatrix} s_2
(d) z = (4, -2, 3, \frac{13}{4})
z = \begin{pmatrix} \frac{1}{2} \\ \\ \end{pmatrix} s_1 + \begin{pmatrix} \frac{1}{4} \\ \\ \end{pmatrix} s_2
