# Highly Complex!

Algebra Level 3

If $$\large \displaystyle z_1 \not= 0, z_2$$ be two complex number such that $$\large \displaystyle \frac{z_2}{z_1}$$ is pure imaginary.

Then find the value of $$\large \displaystyle \left \vert \frac{5z_1 + 7z_2}{5z_1 - 7z_2}\right \vert .$$

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