I don't think so. 7 is not a factor of 8, but let's try it and see.
x = - 7
f(-7) = (-7)^3 - 3(-7)^2 + 2(-7) + 8
f(-7) = -343 - 3(49) + 14 + 8
f(-7) = -484
The graph shows that the x intercept (the one you are interested in) takes place at a little over 3. The calculation shows that when x = -7, the y value is -484 which is nowhere's near 0.
