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 In the equation above, a and b are constants. If . what is the value of a?
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If   =   then  (a+bi) is the number reciprocal to  :
a + bi =   =  ,
and all we need to do is to rid of the denominator in  the fraction  .
For it, multiply the fraction by  .  Since the last fraction is 1, multiplication will not change our number  .
People also say "let us multiply the numerator and the denominator of an original fraction by (3-i) ").
So, we have  
    =  = 
and since  = -1,
=  =  = 0.5 - 0.5*i.
Thus we got  a + bi = 0.5 - 0.5*i.
It implies  a = 0.5,  b = -0.5.  The problem is solved.  Your answer is: a = 0.5,  b = -0.5.
On complex numbers, you have these lessons
    - Complex numbers and arithmetic operations on them
    - Complex plane
    - Addition and subtraction of complex numbers in complex plane
    - Multiplication and division of complex numbers in complex plane
    - Raising a complex number to an integer power
    - How to take a root of a complex number
    - Solution of the quadratic equation with real coefficients on complex domain
    - How to take a square root of a complex number
    - Solution of the quadratic equation with complex coefficients on complex domain
in this site.