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Mathematics 14 Online
OpenStudy (anonymous):

help please need quick repsone

OpenStudy (anonymous):

\[\sqrt -36 \over 2+5i\]

OpenStudy (anonymous):

rationalize the denominator

OpenStudy (anonymous):

@phi @iGreen @Mashy @caitlinnr14 @ganeshie8

OpenStudy (anonymous):

@amistre64

OpenStudy (anonymous):

please show steps

OpenStudy (amistre64):

what does it mean to rationalize something?

OpenStudy (anonymous):

one sec let me think

OpenStudy (anonymous):

getting all the 'radical' signs out of it

OpenStudy (amistre64):

thats part of it sure. but in general, we want to convert something into a rational number. we have a complex number on the bottom that they want converted to a rational real number

OpenStudy (anonymous):

oh

OpenStudy (amistre64):

complex numbers are converted using a conjugate since: (a^2 - b^2) = (a+b)(a-b)

OpenStudy (amistre64):

when b is a pure imaginary value like say 3i a^2 - (3i)^2 = a^2 -9i^2 but i^2 = -1 a^2 -9(-1) = a^2 + 9

OpenStudy (anonymous):

is looks like the same principle from my last question

OpenStudy (anonymous):

ok im starting to understand it

OpenStudy (amistre64):

so, this gives us a similar formula: a^2 + b^2 = (a + bi) (a - bi)

OpenStudy (amistre64):

so using a conjugate we end up with sqrt(-36) 2-5i -------- * ----- 2+5i 2-5i

OpenStudy (anonymous):

so basicly you multiply out the complex terms conjate factors in the denominator to remove the imagery terms

OpenStudy (amistre64):

yep

OpenStudy (anonymous):

ok so that would be the answer

OpenStudy (amistre64):

show me what your solution looks like

OpenStudy (anonymous):

simplified or

OpenStudy (amistre64):

simplified is fine ... ill know if you messed up :)

OpenStudy (anonymous):

simplified it would be 30/29 + 12i / 29

OpenStudy (amistre64):

29 is good now the top, lets chk sqrt(-36) = sqrt(36) sqrt(-1) = 6i 6i(2 - 5i) = 12i -30i^2 = 12i -30(-1) 30+12i ------- 29 :):)

OpenStudy (amistre64):

yours is good

OpenStudy (anonymous):

thx

OpenStudy (amistre64):

yw :)

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