(16)((x^2+1)^3))(1-3x^2)
The only thing that makes this 0 is found in the last term
We have
1 - 3x^2 = 0 add 3x^2 to both sides
1 = 3x^2 divide bpth sides by 3
1/3 = x^2 take the square root of both sides
±√(1/3) = x
And these are the two values that make this function = 0
Notice that (x^2 +1) can never equal 0
Here's a graph.........https://www.desmos.com/calculator/1kvavvdo1i
Notice that there are only two zeroes at x = ±√(1/3)