The equation of the smallest degree with real coefficients having 1 + i as one of the roots is
x22x+2=0
We know that, imaginary roots of a quadratic equation occur in conjugate pair.
It is given, that, 1 + i is one of the roots.
So, the other root will be 1 - i.
Thus, the quadratic equation having roots 1 + i and 1-i is,
x2−(1+i+1−i)x+(1+i)(1−i)=0⇒x2−2x+2=0