To simplify the expression "x²-16 X4 S-√x² +9", we need to first identify and combine like terms, and then simplify any radicals or exponents.

One issue with the given expression is that it contains typographical errors, it should read "lim (x²-16) / (x4 - √x² +9)"

To solve this limit we can factor the numerator and denominator.

= lim (x²-16) / (x²(x²-√x²+9) -9(x²-√x²+9))

= lim (x²-16) / (x4 - √x4 +9x² -9)

Now we can simplify the limit by canceling out the x4 -9 from the numerator and denominator,

= lim (x²-16) / (√x4 -9)

And now we can substitute x=4 and we will get the answer as 0.

lim (x²-16) / (√x4 -9) = lim (4²-16) / (√4² -9) = 0