3) đkxđ : x \(\ne\pm3\)

3) <=> \(x^2-9=16\Leftrightarrow x^2=25=>\left\{{}\begin{matrix}x=-5\\x=5\end{matrix}\right.\)

b) = 325 x ( 1574 - 325 - 249 )

= 325 x 1000 = 325000

c) =321 x (574 + 425 + 1)

  = 321 x 1000 = 321000

d) = 175 x(1274 - 273 -1)

= 175 x 1000 = 175000