The possible rational zeros are +1/1 and +2/1 (which simplify to +1 and +2). Trying these we find that only -2 is actually a zero:
-2 | 1 -4 -11 2
----- -2 12 -2
------------------
1 -6 1 0
The zero in the lower right corner is the remainder. (It is also f(-2)!) Since it is zero then what we divided by (x-(-2)) [or (x+2)] divides evenly. So (x+2) is a factor of f(x). Not only that but the rest of the bottom row tells us what the other factor is. The "1 -6 1" translates into . So now
The other zeros of f(x) will come from the second factor. Since it is a quadratic that won't factor, we can use the quadratic formula:
Simplifying...
which is short for or
So the three zeros for f(x) are: -2, and