Mathematics
10 Online
OpenStudy (anonymous):
Write the expression in standard form.
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OpenStudy (anonymous):
\[\frac{ 7 }{ 3-15i }\]
OpenStudy (anonymous):
@jim_thompson5910
OpenStudy (the_fizicx99):
Standard form?
OpenStudy (anonymous):
I think it's a+bi if a=0 and b can't =0
OpenStudy (the_fizicx99):
Oh ok, sec
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jimthompson5910 (jim_thompson5910):
multiply top and bottom by 3+15i
jimthompson5910 (jim_thompson5910):
the reason why this is done is because (a+bi)(a-bi) = a^2 + b^2 which effectively converts the denominator into a real number
OpenStudy (anonymous):
okay, I got (21+105i)/(9-225i^2) is this right so far?
OpenStudy (anonymous):
Wait... I think I might have it... Is (7+35i)/78 correct?
jimthompson5910 (jim_thompson5910):
225i^2 = 225(-1) = -225
so 9-225i^2 = 9 - (-225) = 9 + 225 = 234
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jimthompson5910 (jim_thompson5910):
(7+35i)/78 is correct after fully simplifying/reducing
OpenStudy (anonymous):
Do you think you could help me with one more?
jimthompson5910 (jim_thompson5910):
sure, go for it
OpenStudy (anonymous):
Find the real numbers x and y that make the equation true.
-3 + yi = x + 6i
OpenStudy (anonymous):
@jim_thompson5910
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jimthompson5910 (jim_thompson5910):
The real part of -3+yi is -3
The real part of x+6i is x
so x = -3 since the real parts are equal
jimthompson5910 (jim_thompson5910):
the imaginary part of -3+yi is yi
the imaginary part of x+6i is 6i
So
yi = 6i
y = 6