Accedmychevron_right11thchevron_rightmathchevron_rightComplex Numberschevron_rightExercise 1.3

Question 1

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Factorize the following .

(viii) 2z222z+652z^2 - 22z + 65

Solution

Find roots using quadratic formula:z=22±4845204=22±364=22±6i4=11±3i2Therefore:2z222z+65=2(z11+3i2)(z113i2)=2(2z113i2)(2z11+3i2)=24(2z113i)(2z11+3i)=12(2z113i)(2z11+3i)\begin{aligned} & \boxed{\text{Find roots using quadratic formula:}} \\ \\ & z = \frac{22 \pm \sqrt{484 - 520}}{4} = \frac{22 \pm \sqrt{-36}}{4} = \frac{22 \pm 6i}{4} = \frac{11 \pm 3i}{2} \\ \\ & \boxed{\text{Therefore:}} \\ \\ & 2z^2 - 22z + 65 = 2\left(z - \frac{11 + 3i}{2}\right)\left(z - \frac{11 - 3i}{2}\right) \\ \\ & = 2\left(\frac{2z - 11 - 3i}{2}\right)\left(\frac{2z - 11 + 3i}{2}\right) \\ \\ & = \frac{2}{4}(2z - 11 - 3i)(2z - 11 + 3i) \\ \\ & = \frac{1}{2}(2z - 11 - 3i)(2z - 11 + 3i) \end{aligned}