# what is magnitude of −3i?

### 11 Answers

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- Anonymous5 months ago
(-3)^2 = 9. Don't listen to the idiots who says it's 3.

- roderick_youngLv 75 months agoReport
The first equation is true, but the "magnitude" of a vector is the absolute value of its length, so 3 is actually correct.

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- 5 months ago
i is the square root of -1. so you'll have to square both of these. In this example: -3*-3 =9 and sqrt(-1)*sqrt(-1) =-1 . So now take 9*-1 to get a final answer of -9

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- PuzzlingLv 75 months ago
Remember:

|a + bi| = √(a² + b²)

In this case, a=0, b=-3

|-3i| = √[(-3)²]

= √9

= 3

Of course if you think of it as the distance from the origin (0,0i) to (0,-3i) on the complex plane, it's obviously just 3, as confirmed by the formula.

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- 5 months ago
It is just 3.

Use pythagoras to find the hypotenuse and ie. the longest side which is the magnitude when you have numbers in both vertical and horizontal components, like -3i+2j.

Also the magnitude is just the positive value of the length of the line/vector, just thought i'd mention.

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