Why does a minus times a minus equal a plus?

Answer 1

it's a fact. use the calculator and you'll get the answer. just remember the fact then you will be able so score high marks already!

Answer 2

Minus Times Minus

Answer 3

The idea seems to be to make it seem intuitively reasonable (rather than merely say “It is an axiom.” ; that is a statement of higher algebra – which, as it stands, is wrong, although it can be proved from the axioms, with some delicate procedures!).

The website listed by detektibgapo has several good illustrations. Some of the replies here are also useful.

My favourite (compare debts) relies on bank transactions: a debit is a negative amount added to your balance. If the bank applies one, or more, debits by mistake, they correct the matter by negating the debit(s).

Also consider an extension of the idea of Jim Caprio, in the website described above:
2 x 3 = 2 + 2 + 2 = 6 Multiply 2 three times - no problem
2 x (-3) = -3 + -3 = -6 Multiply -3 two times - no problem
(-2) x (-3) = ? Confusion! How do you expand this?

Fit that second line into a pattern:
2 x (-3) = -3 + (-3) = -6
1 x (-3) = -3 = -3
0 x (-3) = 0
-1 x (-3) = = +3
-2 x (-3) = = +6

Does that help?

Answer 4

This Site Might Help You.

RE:
Why does a minus times a minus equal a plus?

Answer 5

Not a proof, but a demonstration: 4*-3 = -12 3*-3 = -9 (previous number plus 3) 2*-3 = -6 (previous number plus 3) 1*-3 = -3 (previous number plus 3) 0*-3 = 0 (previous number plus 3) -1*-3 = 3 (previous number minus 3) minus times minus equals plus

Answer 6

If we subscribed to the fact that in speech a double negative is a positive. We must subscribe to the fact that minus times a minus is a plus otherwise there is no such thing as a double negative in speech. Sounds good I guess

Answer 7

You have to visualize a number line with Zero as the center, two arrows headed off in either direction. On the line, whatever number you are in reference on and you use a math operator (-,+,*,/) it changes the point of reference upon that line. The combinations of the math operators prove the truth tables established by Boolean, ie two negatives is the same as true, two positives is the same as true... Only division by Zero is undefined.

Answer 8

Solution:

We know that -1 = -1

=> 1 = -1/-1 (Remember this 1 = -1/-1 (we apply this below))

=> -1 = -1 * (-1/-1) (both side of above equation is multiplied with -1)

=> -1/(-1/-1) = -1

=> 1/(-1*-1) = -1/-1

=> 1/(-1*-1) = 1 (above proved equation 1 = -1/-1 applied)

=> 1 = -1 * -1

For more formulas like this

What is the formula for (a+b+c+d+e+f+g+h)^2

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Answer 9

Multiplying any number times a negative number changes its sign.

So if you want to change the sign of a positive number, multiply it times -1. so : 6*(-1) = -6
If you want to change the sign of a negative number, multiply it times -1. so: (-6)*(-1) = 6

The whole uderlying reason is to give you the ability to change the sign. Later on, in higher mathematics and statistics there are reasons for squaring negative numbers to force all of the terms to be positive.

Answer 10

Imagine the following situation:

You're standing at a street corner. At exactly noon, a car passes by you, going east, at a constant rate of 20 miles/hour. After one hour has elapsed, that is, at 1:00 p.m., it would be 20 miles east of where you're standing. And one hour ago, at 11:00 a.m., it was 20 miles west of where you're standing.

Now, what would it mean if the car was travelling east at -20 miles/hour? It'd be in reverse, going west, of course. So, if it were going at -20 miles/hour east, at 1:00 p.m. it would be 20 miles west of where you're standing. Finally, if it were going -20 miles/hour east, at 11:00 a.m., where would it be? 20 miles east, of course. What does this mean?

(-20 miles/hour)(-1 hour) = 20 miles.

Hence here is a "concrete" explanation of why two negatives multiply to make a positive number.

Answer 11

minus minus equals to plus because its a rule in mathematic multiplication................
-1 * -1 = +1
its is an axiom.....there is no proof for it..................