a) 4x²-9=0
<=>(2x-3).(2x+3)=0
<=>\(\left[ \begin{array}{l}x=3/2\\x=-3/2\end{array} \right.\)
b) √5x-5-√35=0
<=>5x-5-√35=0
<=>x=$\frac{5+√35}{5}$
c) √x²-9=3.√x-3 (đk: x≥3)
⇔x²-9=9.(x-3)
⇔x²-9=9x-27
⇔x²-9x+18=0
⇔(x²-6x)-(3x-18)=0
<=>x(x-6)-3(x-6)=0
<=>(x-6).(x-3)=0
<=>\(\left[ \begin{array}{l}x=6(TM)\\x=3(TM)\end{array} \right.\)
d) √x-2-√x.(x-2)=0 (đk: x≥2)
⇔√x-2=√x.(x-2)
⇔x-2=x.(x-2)
⇔x-2=x²-2x
⇔x²-3x+2=0
⇔(x²-2x)-(x-2)=0
⇔x.(x-2)-(x-2)=0
⇔(x-2).(x-1)=0
⇔\(\left[ \begin{array}{l}x=2(TM)\\x=1(KTM)\end{array} \right.\)
