Tìm x biết: a) \(\sqrt {{{\left( {2{\rm{x}} + 3} \right)}^2}} = 4\); b) \(\sqrt {9{\rm{x}}} - 5\sqrt x = 6 - 4\sqrt x \).

Tìm x biết:

a) \(\sqrt {{{\left( {2{\rm{x}} + 3} \right)}^2}} = 4\);

b) \(\sqrt {9{\rm{x}}} - 5\sqrt x = 6 - 4\sqrt x \).