Answer:
other x values are -5,-4
Step-by-step explanation:
f(x)=0 for x=−6
Apply synthetic division to get the quotient . using that we find other two values of x
-6 1 15 74 120
0 -6 - 54 -120
-------------------------------------------------
1 9 20 0
the quotient is 
now factor the left hand side, product is 20 and sum is 9

So other x values are -5,-4
i believe the answer is concave
U would subtract 2 an 3 from 56 using a variable x
56-2-3=x
X=51
Look at the slope in each equation. A neg. slope indicates that the function is decreasing. A pos. slope: increasing.