Question

Let $z_1=3+4i$ and $z_2=-4+3i$. Then the modulus of $z=z_1+z_2$ is equal to:

• A. $5$
• B. $5\sqrt{2}$
• C. $5\sqrt{3}$
• D. $5\sqrt{5}$

Answer 1

The correct option is B $5\sqrt{2}$

$z_1=3+4i$

$z_2=-4+3i$

$z=z_1+z_2$

$\therefore z=(3+4i)+(-4+3i)$

$\therefore z=(-1+7i)$

$\therefore |z|=5\sqrt{2}$