if u answer this then u r one in a 10,000
By kunalbalani
@kunalbalani (17)
India
June 10, 2007 10:43pm CST
alright....this is something u knw it but don't knw why
...a negative value when multiplied by a negative value gives a positive output...why??
i mean -6*-6=36 WHY NOT -36
7 responses
@AndriaToh (1268)
• Malaysia
11 Jun 07
I obtained the following explanation from Dr. Math forum. Hope it helps.
If we agree that a negative number is just a positive number multiplied by -1.
For example, -3 * -2 = (-1)(3)*(-1)(2) = (-1)(-1)(6)
So, the question is what is
(-1)(-1) = ?
and the convention adopted is (-1)(-1) = 1
The reason why this convention is adopted is because other other conventions would cause something to break.
For example, if we take (-1)(-1) = 1 then the distributive property wouldnt't work.
(-1)(-1 + 1) = (-1)(-1) + (-1)(1)
(-1)(0) = (-1) + (-1)
0 = -2
And so, the convention is (-1)(-1) = 1
Visit www.onlinemathlearning.com for more information on math.
@AndriaToh (1268)
• Malaysia
12 Jun 07
O.k. Let's try again with a specific eg.
Show that -3 * -2 = 6
Step 1: -3 = (-1)(3) and -2 = (-1)(2)
Step 2: -3 * -2 = (-1)(3)* (-1)(2) = (-1)(-1)(3)(2)
Step 3: Is (-1)(-1) = 1 or (-1)(-1) = -1?
Step 4: We show that (-1)(-1) cannot be -1 with the following example:
Let's first assume that (-1)(-1) = -1
(-1)(-1 + 1) = (-1)(-1) + (-1)(1) {Distributive law}
(-1)(0) = -1 + -1
0 = -2 {We get a contradiction}
If we assume (-1)(-1) = 1
(-1)(-1 + 1) = (-1)(-1) + (-1)(1)
(-1)(0) = 1 + -1
0 = 0 {We get a valid equality}
So, the convention adopted is (-1)(-1) = 1
Step 5: In math, (-1)(-1) = 1 is an axiom ie.a statement that is accepted without proof
I've broken the explanation into steps. If you still do not understand let me know which step and then I can explain further.
if you do not know what a distributive rule is visit www.onlinemathlearning/number-properties.html
@kunalbalani (17)
• India
12 Jun 07
hey i couldn't understand ur explanation can u pls help me to understand it....wht u r saying is not wrong but i m just looking for a bit more precise ans...pls do reply
@lillake (1630)
• United States
11 Jun 07
Multiplying by a negative sends the number in the negative direction. Becauss the negative direction of an alrady negative number is positive it makes the answer positive. Think of two magnets, they can either pull towards each other which would be when a positive and negative side meet. Or they can push away from each other, when two negatives meet.
@kunalbalani (17)
• India
12 Jun 07
cool....u r the first one to think abt it seriously........just hang on meet ...u r just using a concept of number line.....multiplication between any two integers give u an area.....i m using over here is a two dimensional example....so try it with a reference co-ordinate x-0-y plane....u r goin in a right direction ..pls do reply if u get 2 know
@srini_the_creator (196)
• India
13 Jun 07
I think you want to plot the point of (-6,-6)
in the X-O-Y plane
in that case the plotted point is in (-,-) quadrant
@HsuYinFung (161)
• United States
11 Jun 07
I had an argument with a co-worker not too long ago about this. His problem was the subtraction of a negative. He thought 11- -6= 5, when of course 11- -6 =17. Subtracting a negative is the same as adding a positive. He finally used a calculator and actually admitted he was wrong.
@kunalbalani (17)
• India
12 Jun 07
it's not a maths rule my frns.....evrything ...evry single logic have some explantions ...some logic behind it m frnd....try it, i m sure will get it....take help if u need it...
@dopey22girl (3319)
• United States
11 Jun 07
Why? I guess I don't know exactly why, but that's just the way it goes. Hmm it's weird when you think about it...
