b: \(\sqrt{8^2+6^2}-\sqrt{16}+\dfrac{1}{2}\sqrt{\dfrac{4}{25}}\)
\(=10-4+\dfrac{1}{2}\cdot\dfrac{2}{5}=6+\dfrac{1}{5}=\dfrac{31}{5}\)
4:
a: căn x-1=3
=>căn x=4
=>x=16
b: căn x-3=2
=>căn x=5
=>x=25
c: 5/12*căn x-1/6=1/3
=>5/12*căn x=1/2
=>căn x=1/2:5/12=1/2*12/5=12/10=6/5
=>x=36/25
d: căn x-1-3=0
=>căn x-1=3
=>x-1=9
=>x=10
e: =>căn x+1=1
=>x+1=1
=>x=0
f: =>|3/5*căn x-1/20|=1/5+3/4=19/20
=>3/5*căn x-1/20=-19/20 hoặc 3/5*căn x-1/20=19/20
=>3/5*căn x=1
=>căn x=5/3
=>x=25/9