Product of Imaginary Numbers

Algebra Level 1

The product of two purely imaginary numbers is always:


Choose the best option.

A real number An imaginary number A rational number An irrational number

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15 solutions

Parveen Soni
Nov 12, 2014

let the two img. number is ia and ib where a and b are two real number. Note that numbers are img. not complex. Now product of two number is (ia)(ib)=ab(i^2). Since i^2=-1 hence we have product as -ab which is a real number. So Product of two img. number is always a real number.

imaginary is also correct answer , real numbers are subsets of imaginary numbers .

Abyn Scaria - 6 years, 6 months ago

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No. Real numbers are a subset of complex numbers, not imaginary numbers.

Hariharan Srikrishnan - 6 years, 6 months ago

real number contains all numbers except img. and complex

Parveen Soni - 6 years, 6 months ago

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but real numbers does not contains imaginary numbers

Naresh Reddy - 6 years, 6 months ago

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@Naresh Reddy updated my statement

Parveen Soni - 6 years, 6 months ago

good question bro

Sundar Rajan Rv - 6 years, 6 months ago

The Real Numbers did not have a name before Imaginary Numbers were thought of. They got called "Real" because they were not Imaginary.

Dina El Okda - 5 years, 11 months ago

real number are subset of complex... so correct ur answer -_-

Manish ßaid - 6 years, 6 months ago

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-_- what? Noob

Sanath Kumar - 6 years, 6 months ago

rational number is also correct. because when there is a product ( from 2 imaginary numbers) it can be expressed as division where the divisor is not zero... therefore it is also correct

Reynaldo Zamora - 6 years, 6 months ago

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The product of i i and 2 i \sqrt{2} i is 2 - \sqrt{2} , which is not rational.

Calvin Lin Staff - 6 years, 6 months ago

The product of two imaginary numbers does not necessarily is a rational or irrational number, but it's always be a real number.

Parveen Soni - 6 years, 6 months ago

i agree with you.

Jhunnel Clamor - 6 years, 6 months ago

read the word always ?....always means for any two imaginary number ....therefore the correct answer is only : real number

Cauchy Pascal - 5 years, 11 months ago
Henrique Ribeiro
Nov 19, 2014

The product of two imaginary numbers does not necessarily is a rational or irrational number, but it's always be a real number.

Muhammad Umair
Nov 18, 2014

Imaginary number contains " i " in it so after multiplication we`ll get i^2 = -1 a real number

Triga Fool
Jun 27, 2015

real and negative

Hari Krishnan
Jun 26, 2015

For eg take two imaginary numbers as i and 2i and the product of these two are -2 which is a real number.

Consider the first imaginary number we learned in school, i, the square root of of negative one. If we square it, we get a real, rational number. So if the product of two imaginary numbers is ALWAYS something, it has to be one of these, since i^2 is one of them. Then consider if you can add a term to one of the i's to make the solution no longer either rational or real. If we multiply sqrt2i x i, then we get a real irrational number. Presuming that the questions offers us a correct answer, it has to be the other one. There is nothing you can add to i such that when you square it you get an imaginary number.

Zuganto Hasan
Nov 19, 2014

real number..........i.e ai bi=-ab (i i=-1) which is real, but for complex number it is imaginary too

Muaz Ali
Nov 19, 2014

Suppose two imaginary numbers 2i and 3i . Then their product is (2i)(3i) which is equal to 6i^2 as we know i^2=-1 so it is -6 which is a real number ......

Abhijeet Anand
Nov 19, 2014

Let two purely imaginary nos. are z1=ai and z2=bi ; a,b in R, then z1*z2 = ab(i^2)=-ab in R; as by definition i^2 =-1.

Naren Raj
Nov 19, 2014

take the example 3i and 4i both are imaginary number now product of these both number is 12i^2 since i^2=-1 then ans will be -12 is puerly real

Charles Victor
Nov 18, 2014

The Product of 2 Imaginary units i.e 'i' is always a negative real number. i * i = -1. Eg : Let 3i and 4i be two imaginary numbers. The product is 12 (i)^2. Now, the value of i^2 will decide whether the result is real or imaginary. Here's the catch : According to the standards of Mathematics, the square of the imaginary unit 'i' is always equal to '-1'. Therefore, we have the solution as '12 (-1) = -12; which thus is a real number. You can test it with different values of imaginary numbers and get the same analysis. Also remember that a 'Complex' number is different from an Imaginary number.Few people multiply complex numbers and show complex numbers as results and say that the result is not always real. :P

product of 2 imaginary numbers is not always a negative real number. eg: -2i*4i=-8(-1)=8.

Anindya Mahajan - 5 years, 11 months ago
Rishaw Sahu
Nov 18, 2014

let us consider any two imaginary number i^n and i^m. then product is i^m+n you can put arbitrary values of m and n .we can get areal number. e.g...m=1 , n=1 then product is i^2=-1 which is real number.

Prestes Bruno
Nov 18, 2014

if i=square root of -1 then root x root will "cancel" each other, it remains -1, which is a real number

Fawad Khan
Nov 18, 2014

i^2=i.i=-1=real number

Melbin Mp
Nov 18, 2014

2i*2i=4i^2=-4 where i^2=-1

Imazinary numbers are always considered as (a+ib) ......... and not only ib

Subham Goyal - 6 years, 6 months ago

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the result should be generalized...why only ix....be taken as example...it should be for (x+iy) ...in that case the prodeuct is always an imaginary no. as all real no. 'r' can be written as r+0i...

Nikhil Rajawat - 6 years, 6 months ago

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a+ib is complex number not imaginary number and question stated that consider purely img. number.

Parveen Soni - 6 years, 6 months ago

a+ib is complex number not imaginary number.

Parveen Soni - 6 years, 6 months ago

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