The roots of the quadratic equation z2+bz+c=0 are 5 + 3i and 5-3i. What is b+c?
Since the quadratic equation has real coefficients and the roots are complex numbers, the roots come in complex conjugate pairs. This means that the other root must be 5−3i.
We can use the fact that the sum of the roots of a quadratic equation is equal to the negative of the coefficient of our z term. In other words, the sum of the roots is b. So, we have:
b=5+3i+(5−3i)=10.
We can also use the fact that the product of the roots of a quadratic equation is equal to the constant term. In other words, the product of the roots is c. So, we have:
c=(5+3i)(5−3i)=52−(3i)2=25+9=34.
Therefore, b + c = 10 + 34 = 44.