Question

solve (x^2+16) (x+5)=0

Answer 1

Remember that if two numbers multiplied together equal 0, then at least one of them must be 0. So, either
\[x^{2}+16=0\]or\[x+5=0\]

The first equation can only be true if \[x^{2}=-16\]
which is impossible (unless you working with complex numbers).

So the only Real answer occurs if x+5=0..which I leave to you.

Answer 2

If your class is learning complex numbers, take the square root ot both sides in the other equation and you'll get the complex answer too.