DK: X>=0
$(=) \sqrt{x} = 4 - \sqrt{2x}$ $(=)x=16-8 \sqrt{2x} + 2x$
$(=) 8\sqrt{2x}= 16+2x-x$
$(=) 8\sqrt{2x}=16+x$
$(=) 64.2x=256+32x+x^2$
$(=) 96x-256-x^2=0$
$(=) x^2 - 96x+256=0$
$(=)\frac{-(-96±\sqrt{(-96)^2-4.1.256} )}{2.1}$
$(=)x=\frac{96±\sqrt{8192} }{2}$ $(=)\frac{96±2^6\sqrt2}{2}$
$(=) x=\frac{96+64\sqrt2}{2}$ hoặc $\frac{96-64\sqrt2}{2}$
$(=) x= 48+32\sqrt2$(nhân) hoặc $x=48-32\sqrt2$(loại)
$=) x=48-32\sqrt2$
