Quick Exponent Question

[goldberry]

The way I learned exponents was like this: If the exponent was written - (3^2) then you took 3^2 first, then applied the negative to the answer. If it was written -3^2, then that meant -3 x -3 which would be positive 9.

 

DD is doing TT, and they are saying -3^2 is -9. No parentheses.

 

Did I learn this incorrectly?

 

Thanks!

[dirty ethel rackham]

TT is correct. The exponent is done before applying the negative, which is basically multiplying by -1. According to the PEDMAS rule, the exponent is done before multiplication. (-3)^2 would be 9. -3^2 would be 1(3)(3) = (-1)(3)(3). If you do a quick Google search of muliplying exponents with negative numbers, you'll find lots of information on this.

[regentrude]

The way I learned exponents was like this: If the exponent was written - (3^2) then you took 3^2 first, then applied the negative to the answer. If it was written -3^2, then that meant -3 x -3 which would be positive 9.

 

DD is doing TT, and they are saying -3^2 is -9. No parentheses.

 

Did I learn this incorrectly?

 

Exponent precedes multiplication.

-3^2 is -(3^2)= - 9

If they wanted (-3)*(-3), it would have to be written as (-3)^2 which would equal 9.

[goldberry]

Thanks so much!

[Dana]

I also like to illustrate it like this...

 

15 - 3^2

 

The next step is clearly

15 - 9

 

So if the 15 weren't there,

-3^2 = - 9.

The base is 3, then we're taking the opposite of it.

 

Testing on this tonight... wanna bet a number of students still get it wrong...even with the calculator? (Sigh.)

Interestingly... depending on the model of calculator, some will do this incorrectly... or (more accurately), you've got to be VERY careful with how your calculator does operations to trust it with some types of arithmetic! (Lies my calculator told me...)