SOLUTION: {{{((3+i)/(2-i))(a+bi)=1}}} In the equation above, a and b are constants. If {{{i=sqrt(-1)}}}. what is the value of a?

Algebra ->  Expressions -> SOLUTION: {{{((3+i)/(2-i))(a+bi)=1}}} In the equation above, a and b are constants. If {{{i=sqrt(-1)}}}. what is the value of a?      Log On


   



Question 1043213: %28%283%2Bi%29%2F%282-i%29%29%28a%2Bbi%29=1 In the equation above, a and b are constants. If i=sqrt%28-1%29. what is the value of a?
Found 2 solutions by stanbon, ikleyn:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
((3+i)/(2-i))(a+bi)=1 In the equation above, a and b are constants. If i=sqrt(-1). what is the value of a?
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(6-3i+2i+1)(a+bi) = 1
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(7-i)(a+bi) = 1 + 0i
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7a+b + (7b-a)i = 1 + 0i
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7a + b = 1
-a + 7b = 0
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Modify for elimination::
7a + b = 1
-7a + 49b = 0
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Add and solve for "b"::
50b = 1
b = 1/50
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Solve for "a":
7a + b = 1
7a = (49/50)
a = 7/50
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Cheers,
Stan H.
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Answer by ikleyn(52865) About Me  (Show Source):
You can put this solution on YOUR website!
.
%28%283%2Bi%29%2F%282-i%29%29%28a%2Bbi%29=1 In the equation above, a and b are constants. If i=sqrt%28-1%29. what is the value of a?
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If  %28%283%2Bi%29%2F%282-i%29%29%28a%2Bbi%29 = 1  then  (a+bi) is the number reciprocal to  %28%283%2Bi%29%2F%282-i%29%29:


a + bi = 1%2F%28%28%283%2Bi%29%2F%282-i%29%29%29  =  %282-i%29%2F%283%2Bi%29,


and all we need to do is to rid of the denominator in  the fraction  %282-i%29%2F%283%2Bi%29.

For it, multiply the fraction by  %283-i%29%2F%283-i%29.  Since the last fraction is 1, multiplication will not change our number  %282-i%29%2F%283%2Bi%29.
People also say "let us multiply the numerator and the denominator of an original fraction by (3-i) ").


So, we have  

   %282-i%29%2F%283%2Bi%29 = %28%282-i%29%2A%283-i%29%29%2F%28%283%2Bi%29%2A%283-i%29%29 = %282%2A3+-2i+-+3i+%2B+i%5E2%29%2F%283%5E2+-+i%5E2%29

and since i%5E2 = -1,

= %286+-+5i+-+1%29%2F%289%2B1%29 = %285-5i%29%2F10%29 = 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.