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-1^2?! (binomial help!)

Was just doing some binomial expansion work expanding (2-x)^6

6C0 * 2^6 * (-x)^0 = 64
6C1 * 2^5 * (-x)^1 = -192x

6C2 * 2^4 * (-x)^2 = 15*16*-1^2*x^2

I typed the last line into my calculator, and I got -240x^2... But doesn't
-1^2 = 1 ?!?!?

so I typed that in, and -1^2 = -1. But if I type in -1*-1 = 1.

What is going on? Have I made a rookie error somewhere? Why is my calculator telling me the answer is negative instead of positive? I was taught anything negative squared is positive!

Is this a case of having to work out the negative power in my head, e.g odd power = negative and even power = positive?
Reply 1
Avatar for f1mad
f1mad
13
Put in brackets...

(-1)^2.
Reply 2
Avatar for mrdoovde1
mrdoovde1
17
When doing on the calculator it does -(1)^2 i.e. it squares 1 first and the adds the minus sign. As mentioned above, put the entire -1 in brackets.
Original post by lollage123
Was just doing some binomial expansion work expanding (2-x)^6

6C0 * 2^6 * (-x)^0 = 64
6C1 * 2^5 * (-x)^1 = -192x

6C2 * 2^4 * (-x)^2 = 15*16*-1^2*x^2

I typed the last line into my calculator, and I got -240x^2... But doesn't
-1^2 = 1 ?!?!?

so I typed that in, and -1^2 = -1. But if I type in -1*-1 = 1.

What is going on? Have I made a rookie error somewhere? Why is my calculator telling me the answer is negative instead of positive? I was taught anything negative squared is positive!

Is this a case of having to work out the negative power in my head, e.g odd power = negative and even power = positive?


A negative squared is a positive :smile: but wehn you input -1^2, your calculator thinks you want to do -(1)^2, which would be -1.

I do most of them in my head, or work them out individually to avoid mistakes such as that :smile:

Hope I helped
(edited 12 years ago)
Casio calculators do this, others don't. It is the way the calculator carries out the order of operations.

You can make it work by using brackets (−1)2(-1)^2 or using the ANS button.

Type -1 =

ANS2=ANS^2=

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