Why doesn't √-1×√-1 always equal 1 in complex numbers?

In summary, the conversation reveals that while the rule √a√b = √ab holds for nonnegative real numbers, it does not hold for complex numbers. This can be seen through examples such as √-5×√-5=5 and √-1×√-1=1 not being true. This is due to the fact that √-1 is equal to the imaginary number i, and i^2 is equal to -1, which causes the rule to not hold true.
  • #1
Gourav kumar Lakhera
2
0
As we know that √-5×√-5=5 i.e multiplication with it self
My question is that according to this √-1×√-1=1.but it does not hold good in case of i(complex number).
I.e i^2 =-1. Why?
 
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  • #2
Gourav kumar Lakhera said:
As we know that √-5×√-5=5
No, this is not true. ##\sqrt{-5} = i\sqrt{5}## so ##\sqrt{-5} \cdot \sqrt{-5} = i^2 (\sqrt{5})^2 = -5##, not 5 as you show above.
Gourav kumar Lakhera said:
i.e multiplication with it self
My question is that according to this √-1×√-1=1
This isn't true, either, for the same reason as above.
Gourav kumar Lakhera said:
.but it does not hold good in case of i(complex number).
I.e i^2 =-1. Why?

You are apparently using the rule that ##\sqrt a \sqrt b = \sqrt{ab}##. That rule holds only when both a and b are nonnegative real numbers.
 
  • #3
Thnkuu buddy
 

Related to Why doesn't √-1×√-1 always equal 1 in complex numbers?

1. What are complex numbers?

Complex numbers are numbers that contain both a real part and an imaginary part. They are written in the form a + bi, where a is the real part and bi is the imaginary part, with i representing the square root of -1.

2. How are complex numbers used in science?

Complex numbers are used in various fields of science, including physics, engineering, and mathematics. They are used to represent quantities that have both a magnitude and a direction, such as alternating current in electrical engineering and wave functions in quantum mechanics.

3. What is the purpose of the imaginary unit i in complex numbers?

The imaginary unit i is an essential part of complex numbers as it allows us to represent and manipulate quantities that involve the square root of -1. It also helps in solving equations that do not have real solutions.

4. Can complex numbers be plotted on a graph?

Yes, complex numbers can be plotted on a graph known as the complex plane. The horizontal axis represents the real part, and the vertical axis represents the imaginary part. This allows for a visual representation of complex numbers and their relationships.

5. How are complex numbers added and multiplied?

To add complex numbers, we simply add their real and imaginary parts separately. To multiply complex numbers, we use the FOIL method (First, Outer, Inner, Last) or the distributive property. We also use the fact that i squared equals -1 to simplify the result.

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