Q. Express as a complex number in simplest a+bi form:−3−i−2+9iAnswer:
Multiply by conjugate: Multiply the numerator and denominator by the conjugate of the denominator to remove the imaginary unit from the denominator.The conjugate of (−3−i) is (−3+i).−3−i−2+9i×−3+i−3+i
Apply distributive property: Apply the distributive property (FOIL method) to both the numerator and the denominator.Numerator: (−2+9i)(−3+i)=(−2)(−3)+(−2)(i)+(9i)(−3)+(9i)(i)Denominator: (−3−i)(−3+i)=(−3)(−3)+(−3)(i)+(−i)(−3)+(−i)(i)
Perform multiplication: Perform the multiplication for both the numerator and the denominator.Numerator: 6−2i−27i−9i2Since i2=−1, we have −9i2=9.Numerator becomes: 6−2i−27i+9Denominator: 9−3i+3i−i2Since i2=−1, we have −i2=1.Denominator becomes: 9+1
Combine like terms: Combine like terms in both the numerator and the denominator.Numerator: (6+9)−(2i+27i)=15−29iDenominator: 9+1=10
Write in a+bi form: Write the complex number in a+bi form by dividing the real and imaginary parts by the denominator.Real part: 1015=1.5Imaginary part: 10−29i=−2.9iSo, the complex number in a+bi form is 1.5−2.9i.
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