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More from Complex Numbers and Quadratic Equations

Value of Absolute Square of Complex Number with Real Fraction

Let zz be a complex number with non-zero imaginary part. If 2+3z+4z223z+4z2\frac{2 + 3z + 4z^2}{2 - 3z + 4z^2} is a real number, then the value of z2|z|^2 is ________.

Official Numerical Answer0.5

Step-by-Step Solution

Let the given expression be denoted as w=2+3z+4z223z+4z2=1+62z3+4zw = \frac{2 + 3z + 4z^2}{2 - 3z + 4z^2} = 1 + \frac{6}{\frac{2}{z} - 3 + 4z}. For ww to be a real number, the quantity 2z+4z\frac{2}{z} + 4z must also be real, which implies 2z+4z=2zˉ+4zˉ\frac{2}{z} + 4z = \frac{2}{\bar{z}} + 4\bar{z}. Rearranging this equality gives (zzˉ)(2z24)=0(z - \bar{z})\left(\frac{2}{|z|^2} - 4\right) = 0. Since zz has a non-zero imaginary part, zzˉ0z - \bar{z} \neq 0, leading directly to z2=12=0.5|z|^2 = \frac{1}{2} = 0.5.