Question 119261
Typically, I start at x=0 and move up by 1.
0	-20
1	-6
2	14
3	40
4	72
5	110
6	154
I see there is a zero between x=1 and x=2. 
Then go back the other direction. 
-1	-28
-2	-30
-3	-26
-4	-16
-5	0
The second zero is easy to find at x=-5. 
You can then go from x=1 to x=2 in increments of 0.1 to get more detail.
1.0	-6.0
1.1	-4.3
1.2	-2.5
1.3	-0.6
1.4	1.3
Now between x=1.3 and x=1.4.
Again, keep getting finer and finer.
1.31	-0.4
1.32	-0.3
1.33	-0.1
1.34	0.1
Now between x=1.33 and x=1.34.
You can keep going...