Umn=100V a, Rtđ b, CĐDĐ qua mỗi điện trở 

giúp vs 

a, A =\(\left(5\sqrt{2}-2\sqrt{5}\right).\sqrt{5}-\sqrt{250}\)

       = \(\sqrt{5^2.10}-\sqrt{10}-\sqrt{5^2.10}\)

       =  \(5\sqrt{10}-10-5\sqrt{10}\)

       =  \(-10\)

helpppp

a, rút gọn 

helppp 

help :)) 

-tìm x-

1, \(\sqrt{4-4x+x^2}=3\)

2, \(\sqrt{x^2-6x+9}=1\)

3, \(\sqrt{25-10x+x^2}=1\)