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The roots of the quadratic equation $z^2 + az + b = 0$ are $-7 + 2i$ and $-7 - 2i$. What is $a+b$?

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 Apr 2, 2020
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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?

 Apr 2, 2020

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