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Indices Help [Factorisation & Simplication]

Hello, I am new to this website. Can you people provide me the steps to finding the answers to these questions shown below?

1) 4^x - 9

2) 4^x - 25

3) 16 - 9^x

4) 2^n (n+1) + 2^n (n-1)

5) 3^n (n-1/6) - 3^n (n+1/6)

Thank you very much

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@ZXLPK42

Can you please use more brackets as it's not entirely clear what you mean.

Also, the rules of indices will help

Reply 2
Original post by ZXLPK42
Hello, I am new to this website. Can you people provide me the steps to finding the answers to these questions shown below?

1) 4^x - 9

2) 4^x - 25

3) 16 - 9^x

4) 2^n (n+1) + 2^n (n-1)

5) 3^n (n-1/6) - 3^n (n+1/6)

Thank you very much


You havent actually told us what the question is? There are 5 expressions, what has to be done with each one?
Original post by nerak99
You havent actually told us what the question is? There are 5 expressions, what has to be done with each one?


First 3 is factorise, last two is simplify.
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Original post by Kvothe the arcane
@ZXLPK42

Can you please use more brackets as it's not entirely clear what you mean.

Also, the rules of indices will help

Original post by ZXLPK42
First 3 is factorise, last two is simplify.


first 3 think about diff of 2 squares, use the fact that (a2)x=(ax)2 \displaystyle (a^2)^x = (a^x)^2 to help

last 2 factor out the "power" term first and see what you';re left with, then finish it off
(edited 8 years ago)
Original post by ZXLPK42
Capture.JPG


But 4x=(22)x4^x=(2^2)^x and similarly 9x=(32)x9^x=(3^2)^x

A few questions seem to want you to use the difference of two squares: a2b2=(ab)(a+b)a^2-b^2=(a-b)(a+b)

You can factor out something for the last two expressions.
(edited 8 years ago)
Original post by DylanJ42
first 3 think about diff of 2 squares, use the fact that (a2)x=(ax)2 \displaystyle (a^2)^x = (a^x)^2 to help

last 2 factor out the "power" term first and see what you';re left with, then finish it off


So for example for the first one, do I turn 4^x - 9 into 2^2x - 3^2, and make it equate to (2^x - 3)^2?

And (e.g.) for the fourth one can I turn "2^n (n+1) + 2^n (n-1)" into 2^n (n + 1 + n - 1), and make it so that 2^n (2n)?
Original post by Kvothe the arcane
But 4x=(22)x4^x=(2^2)^x and similarly 9x=(32)x9^x=(3^2)^x

A few questions seem to want you to use the difference of two squares: a2b2=(ab)(a+b)a^2-b^2=(a-b)(a+b)

You can factor out something for the last two expressions.


4x - 9 = 22x - 32 = (2x - 3)2?
Original post by ZXLPK42
So for example for the first one, do I turn 4^x - 9 into 2^2x - 3^2, and make it equate to (2^x - 3)^2?


No to the bolded. While 4x9=22x324^x-9=2^{2x}-3^2, 22x32(2x3)22^{2x}-3^2 \neq (2^x - 3)^2.

What you have to notice that they are both squared terms. And there is a difference between them.
Original post by Kvothe the arcane
No to the bolded. While 4x9=22x324^x-9=2^{2x}-3^2, 22x32(2x3)22^{2x}-3^2 \neq (2^x - 3)^2.

What you have to notice that they are both squared terms. And there is a difference between them.


So is the final step of the solution 22x - 32?
Original post by ZXLPK42
So is the final step of the solution 22x - 32?


No because you can simplify it if you know that a2b2=(a+b)(ab)a^2-b^2=(a+b)(a-b) as I mention above :smile:.

Original post by ZXLPK42
And (e.g.) for the fourth one can I turn "2^n (n+1) + 2^n (n-1)" into 2^n (n + 1 + n - 1), and make it so that 2^n (2n)?
Yes, but I'm not sure if they'd want you to express that as 2n+1n2^{n+1}n but what you've said is correct :smile:.
(edited 8 years ago)
Original post by ZXLPK42
So for example for the first one, do I turn 4^x - 9 into 2^2x - 3^2, and make it equate to (2^x - 3)^2?

And (e.g.) for the fourth one can I turn "2^n (n+1) + 2^n (n-1)" into 2^n (n + 1 + n - 1), and make it so that 2^n (2n)?


4x9 \displaystyle 4^x - 9 into 22x32 \displaystyle 2^{2x} - 3^2 , this is correct, id probably rewrite it further as (2x)232 \displaystyle (2^x)^2 - 3^2 just to see the squared terms easier

... and make it equate to (2^x - 3)^2? this is not right though

remember that a2b2=(a+b)(ab) \displaystyle a^2 - b^2 = (a+b)(a-b)

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4th one looks good, although I would factor out another 2
Original post by Kvothe the arcane
No because you can simplify it if you know that a2b2=(a+b)(ab)a^2-b^2=(a+b)(a-b) as I mention above :smile:.


So does the equation become (2x-3)(2x+3)?
Original post by ZXLPK42
So does the equation become (2x-3)(2x+3)?


Yes :biggrin:. Although what you have above are expressions and not equations as there is no equals (=) sign. Your meaning is clear, however. I just wanted to point that out.
(edited 8 years ago)
Original post by DylanJ42
4x9 \displaystyle 4^x - 9 into 22x32 \displaystyle 2^{2x} - 3^2 , this is correct, id probably rewrite it further as (2x)232 \displaystyle (2^x)^2 - 3^2 just to see the squared terms easier

... and make it equate to (2^x - 3)^2? this is not right though

remember that a2b2=(a+b)(ab) \displaystyle a^2 - b^2 = (a+b)(a-b)

.
.
.

4th one looks good, although I would factor out another 2


How would 2^n(2n) look like if I factored out another 2? I'm not sure if it can be equated as: 2[(2n)^n], but I think it'll be the same as the one above [(2^n(2n)]
Original post by Kvothe the arcane
Yes :biggrin:. Although what you have above are expressions and not equations as there is no equals (=) sign. Your meaning is clear, however. I just wanted to point that out.


Thank you very much for helping me out.
Original post by ZXLPK42
How would 2^n(2n) look like if I factored out another 2? I'm not sure if it can be equated as: 2[(2n)^n], but I think it'll be the same as the one above [(2^n(2n)]


remember that 2n \displaystyle 2^n means 2 x 2 x 2 x 2 x 2... x 2 'n' times, so multiply that by 2 again and you'll get 2 x 2 x 2 x 2 'n+1' times, so yor answer will be...

(this is the answer, so think about it yourself first)

Spoiler

Original post by DylanJ42
remember that 2n \displaystyle 2^n means 2 x 2 x 2 x 2 x 2... x 2 'n' times, so multiply that by 2 again and you'll get 2 x 2 x 2 x 2 'n+1' times, so yor answer will be...

(this is the answer, so think about it yourself first)

Spoiler



I am able to understand the first part, but how does the original value 2n change to n from "2^(n+1) x n"?
Original post by ZXLPK42
I am able to understand the first part, but how does the original value 2n change to n from "2^(n+1) x n"?


so we have 2n(2n) \displaystyle 2^n (2n)

If you had a=bcd \displaystyle a =bcd you could write this as a=cbd=dbc=bdc \displaystyle a =cbd = dbc = bdc etc etc, ie it doesnt matter what order the letters are in.

Using this, we can rewrite the first expression as (2)2n(n) \displaystyle (2)2^n(n)

2×2n=2n+1 \displaystyle 2 \times 2^n = 2^{n+1}

2×2n×n=2n+1×n \displaystyle \therefore 2 \times 2^n \times n = 2^{n+1} \times n

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