(left{ begin{array}{l}{u_1} - {u_3} + {u_5} = 10\{u_1} + {u_6} = 17end{array} right.)
Giải chi tiết:
(left{ begin{array}{l}{u_1} - {u_3} + {u_5} = 10\{u_1} + {u_6} = 17end{array} right. Leftrightarrow left{ begin{array}{l}{u_1} + d - {u_1} - 2d + {u_1} + 4d = 10\{u_1} + {u_1} + 5d = 17end{array} right.)
( Leftrightarrow left{ begin{array}{l}{u_1} + 3d = 10\2{u_1} + 5d = 17end{array} right. Leftrightarrow left{ begin{array}{l}{u_1} = 1\d = 3end{array} right.).