CBSE Class 11-science Answered
Why is - multiplied by - = +? Plz explain both by algebraic and co-ordinate system.
Asked by mmishra23 | 29 Apr, 2009, 05:22: PM
Expert Answer
In the method you gave n(-1)(-1)=(1/n)(-1) = n
It should have been (n-1)-1 = (1/n)-1 = n which leads to prove that reciprocal of reciprocal is number itself
Here is a method to prove algebraically
Basically we need to find
(-1)(-1) = ?
The possible values could be -1 or +1
and the answer is that the following convention has been adopted:
(-1)(-1) = +1
For example, if we adopted the convention that
(-1)(1 + -1) = (-1)(1) + (-1)(-1)
(-1)(0) = -1 + -1
0 = -2
Which is contradiction hence(-1)(-1) = +1
Answered by | 05 May, 2009, 04:04: PM
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