Đề bài

Giải các hệ phương trình

a) $\left\{ {\begin{array}{*{20}{c}}{4x + y = 2}\\{\frac{4}{3}x + \frac{1}{3}y = 1}\end{array}} \right.$

b) $\left\{ {\begin{array}{*{20}{c}}{x - y\sqrt 2 = 0}\\{2x + y\sqrt 2 = 3}\end{array}} \right.$

c) $\left\{ {\begin{array}{*{20}{c}}{5x\sqrt 3 + y = 2\sqrt 2 }\\{x\sqrt 6 - y\sqrt 2 = 2}\end{array}} \right.$

d) $\left\{ {\begin{array}{*{20}{c}}{2(x + y) + 3(x - y) = 4}\\{(x + y) + 2(x - y) = 5}\end{array}} \right.$