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Lesson 5: Exponents with negative bases

# Even & odd numbers of negatives

We can figure out whether multiplication and division problems give us a positive or negative result by thinking about how many negative numbers are used in the computation.

## Want to join the conversation?

• Pos times a pos=pos right?
• Yes, lets say that you have a pos 7 and a pos 5, if you multiply it, it will be a pos 35
• My old maths teacher (who is now looking for a new job in a different country because of us)taught us this trick: (- is bad people)(+ is good
people)
+ PLUS + = Good things happening to the good people is bloody jolly good.
- PLUSE + = Bad things happening to the good people is bloody unfair.
- PLUSE - = Bad things happening to the bad people is bloody jolly good.
+ PLUSE - = Good things happening to the bad people is bloody unfair.
Our current maths teacher called her crazy when we told her how she taught us that.
• It makes sense though.
• hi there, in one of the questions I got -11 to the power of 2, I wrote 121 as my answer, as u said if its a even number its going to be positive, but somehow I got it wrong?
• This is a bit tricky. When there are no parentheses, the negative sign is not part of the base and is instead attached in the last step. So -11^2 = -121. If the problem instead had said (-11)^2, then 121 would have been correct.

Have a blessed, wonderful day!
• same signs=positive
different signs=negative
• these comments are as Ancient as time lol
• why is it that negative and negative =positive, positive and positive= positive, negative and positive =negative, positive and negative= negative
• - and - combine to make a + sign'
• How does all this negative and positive multiplying relate to actual life?
• There are some great explanations about how negation works IRL, and here are some examples for you. Hope it helps!

Paying bills
Let's say you get five bills in the mail for seven dollars each. You'd have 5 x -7 dollars, or -35 more dollars, i.e. 35 fewer dollars.
But what if you had sent out five bills instead of getting them? Then, in a sense, you'd have gotten negative five bills, so you'd have -5 x -7 = 35 more dollars than you started with.

Imagine that you buy five gift certificates worth \$5 each and pay for them using your credit card. You now owe money, so that's -\$25.
The bill comes from the credit card company, but I take it away from you and insist on paying it. You now have \$25 worth of gift certificates without having paid anything.

Taking away a debt is analogous to negating a negative. Taking away five debts of \$5 (-5*-5) equals a gain of \$25.

*Source:* http://mathforum.org/dr.math/faq/faq.negxneg.html
• why is it that negative and negative =positive, positive and positive= positive, negative and positive =negative, positive and negative= negative
• how do you solve fractions
• Okay here's an example, (-2/3)^2 which would be the same thing as -2/3 * -2/3, and you just multiply across so -2/3 * -2/3 = 2*2/3*3, and remember, 2 negatives multiplied equals a positive
• You would get the same answer is you used pos instead of negs right?

EXAMPLE:
Odd # of Pos = Neg
Even # of Pos = Pos

Right?