Question 1207475
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The general theorem of algebra states that if a polynomial with real coefficients
has a complex number root  a+bi,  b=/= 0,  then it has another complex number root  a-bi,  too.


According to this theorem,  if  4-i  is the root of your quadratic equation with real coefficients,
then it has the root  4+i,  too.   It is your other root.