1)tính kết quả:
a, A=\(2\times\sqrt{a}-3\times\sqrt{16}+5\times\sqrt{31}\)
b, B=\(\left(\sqrt{\frac{1}{16}}+\sqrt{\frac{4}{25}}\right)\div\sqrt{\frac{25}{36}}\)
c, \(\left(\sqrt{5}\right)^2-\left(2\times\sqrt{3}\right)^2+\left(4\times\sqrt{2}\right)^2\)