Giải các hệ phương trình:
a) (left{ {begin{array}{*{20}{c}}{3x + 2y = 7}{x - 7y = - 13}end{array}} right.)
b) (left{ {begin{array}{*{20}{c}}{4x + y = 2}{8x + 3y = 5}end{array}} right.)
c) (left{ {begin{array}{*{20}{c}}{5x - 4y = 3}{2x + y = 4}end{array}} right.)
d) (left{ {begin{array}{*{20}{c}}{3x - 2y = 10}{x - frac{2}{3}y = 3frac{1}{3}}end{array}} right.)
Xem chi tiết ♍