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How do you simplify this: (4-8i)(-7+i)?

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rosey-girl | Student, Grade 12 | Valedictorian

Posted August 20, 2013 at 12:02 AM via web

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How do you simplify this: (4-8i)(-7+i)?

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baxthum8 | High School Teacher | (Level 3) Associate Educator

Posted August 20, 2013 at 12:12 AM (Answer #1)

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Use FOIL (first outer inner last) or distributive property

First `4*-7 = -28`

Outer `4*i = 4i`

Inner `-8i*-7 = 56i`

Last `-8i*i = -8i^2`

however  `i^2 = -1`

therefore `-8i^2= +8`

add everything together by combining like terms

-20 +60i

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