Since the roots are -7 + 2i and -7 - 2i,
the equation can be written as: [ z - (-7 + 2i) ] · [ z - (-7 - 2i) ] = 0
or: (z + 7 - 2i)(z + 7 +2i) = 0
When these two factors are multiplied out, the values of a and b can be found.
Can you multiply out these factors?