√-9 × √ -49 Everyone thought the answer was 21 and got it wrong. Can you do it right?

[@richardking5222]

-21, that is straightforward.

[@gheffz]

Phew, did it in me head and glad I was right. Thanks, good video.

[@anatolykatyshev9388]

21 is also correct.
sqrt(-9)=+-3i
sqrt(-49)=+-7i
-3i*7l=21

[@gavindeane3670]

No. The radical symbol is more precisely defined than that.
±√(-9) is ±3i
√(-9) is 3i

[@Sesquipedalian3]

me before watching the video: "haha you guys are stupid, it's obviously 21i"

[@pandurangaraonimmagadda9966]

3i.7i=21i sqr=-21

[@grafrotz5286]

complex squareroot has 2 solutions, thus +21 and -21 are both proper solutions

[@Allahcc31g]

X = -4

[@agronxhelali1250]

3×7=21😊😊

[@michaellyndon6982]

3i*7i=-21

[@KW-gb9cd]

√(-3²) · √(-7²) = 3 · i · 7 · i = -21.

[@pelasgeuspelasgeus4634]

😂😂😂 Absurd, ridiculous, completely useless.

[@johnchastain7890]

These notation tricks are boring.

[@agronxhelali1250]

441🎉🎉😊