Answer:
x = -7, multiplicity 2.
Writing it as a set it is {-7, -7}.
Step-by-step explanation:
(x + 7)(x + 7 )= 0
When 2 expressions are multiplied and the result is zero either of them can be zero, so
x + 7 = 0
x = -7.
In this case, since the 2 factors are the same, there are duplicate roots.
We write this as x = -7, multiplicity 2.