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Mathematics 10 Online
OpenStudy (anonymous):

Write the expression in standard form.

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

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

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

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

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