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Algebra Difficulty 2.9 Junior Find the answer

Find the value of the complex number 2i(3i)=\dfrac{2}{i(3-i)}=(     ), where ii is the imaginary unit.

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Solution

Step 1: Multiply both the numerator and the denominator of the given complex number by the conjugate of the denominator.

2i(3i)=23i+1×3i13i1\dfrac{2}{i(3-i)} = \dfrac{2}{3i + 1} \times \dfrac{3i - 1}{3i - 1}

Step 2: Simplify the expression by applying the distributive property and the fact that i2=1i^2 = -1.

2(3i1)(3i+1)(3i1)=6i29i21=6i291=6i210\dfrac{2(3i - 1)}{(3i + 1)(3i - 1)} = \dfrac{6i - 2}{9i^2 - 1} = \dfrac{6i - 2}{-9 - 1} = \dfrac{6i - 2}{-10}

Step 3: Separate the fraction into real and imaginary parts.

6i210=210+610i=15+35i\dfrac{6i - 2}{-10} = -\dfrac{2}{10} + \dfrac{6}{10}i = -\dfrac{1}{5} + \dfrac{3}{5}i

Step 4: Express the result in the form a+bia + bi.

2i(3i)=15+35i=13i5\dfrac{2}{i(3-i)} = -\dfrac{1}{5} + \dfrac{3}{5}i = \boxed{\dfrac{1{-}3i}{5}}

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.