Always helps me to look at the function's graph. http://graphsketch.com/ is great for this. Here's the graph of your example.
Here you can clearly see that the zero of this function - the point at which the graph crosses the x axis - is 5.
Is there something in particular you're struggling with?
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From start to finish I've made you feel this
Uncomfort in turn with the world you've learned
To love through this hate to live with its weight
A burden discerned in the blood you taste