Question

The value of k for which z1 + kz2 is purely real if z1 = 4+7i and z2 = 1-i is

Answer 1

Answer:

The answer is $k=7$

Step-by-step explanation:

Given $z_1=4+7i$ and $z_2=1-i$

Thus $z_1+kz_2=(4+7i)+k(1-i)=(4+k)+i(7-k))$

Now Since $z_1+kz_2$ is purely real , so imaginary part should be zero

     $\Rightarrow 7-k=0\Rightarrow k=7$