(c + 7)*(c - 7)
(c + 7)*(c - 1*7)
1*(c + 7)*(c - 7)
(1*(c + 7))*(c - 7)
2 -49 + c
-49 + c^2
(7.0 + c)*(-7.0 + c)
(-7 + c)*(7 + c)