# Prove Question help

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Thread starter 2 years ago
#1
mathswatch question:
Prove,using algebra, that the difference between the squares of consecutive odd numbers is always a multiple of 8.

It is out of three but i keep on getting 2 even though i used the correct method:
2n+1+2n+3
(2n+1)²-(2n+3)²
-8n-8
-8(n+1)
-8(n+1) will always be a multiple of 8 to the difference between the squares of consecutive odd numbers(with or without this last statement i get 2 marks)

I NEED HELP URGENTLY!!! THANKS
0
2 years ago
#2
(Original post by basher2475)
mathswatch question:
Prove,using algebra, that the difference between the squares of consecutive odd numbers is always a multiple of 8.

It is out of three but i keep on getting 2 even though i used the correct method:
2n+1+2n+3
(2n+1)²-(2n+3)²
-8n-8
-8(n+1)
-8(n+1) will always be a multiple of 8 to the difference between the squares of consecutive odd numbers(with or without this last statement i get 2 marks)

I NEED HELP URGENTLY!!! THANKS

Where is this question from?
1
Thread starter 2 years ago
#3
(Original post by mitchell2000)
Where is this question from?
NVM i tried a different way and got it right
1
2 years ago
#4
(Original post by basher2475)
mathswatch: algebraic proof
If it's out of three marks and you're saying that what you have is only worth two marks them I'm afraid I'm stumped xD! I can't see what else needs to be doing?

Perhaps showing your working multiplying out the brackets and then simplifying would be a mark?
0
2 years ago
#5
(Original post by basher2475)
mathswatch question:
Prove,using algebra, that the difference between the squares of consecutive odd numbers is always a multiple of 8.

It is out of three but i keep on getting 2 even though i used the correct method:
2n+1+2n+3
(2n+1)²-(2n+3)²
-8n-8
-8(n+1)
-8(n+1) will always be a multiple of 8 to the difference between the squares of consecutive odd numbers(with or without this last statement i get 2 marks)

I NEED HELP URGENTLY!!! THANKS
"Difference" means positive difference, i.e. the larger minus the smaller - for example, the difference between 5 and 7 is 2, not -2. Similarly here, you should be doing (2n+3)^2-(2n+1)^2, rather than (2n+1)^2-(2n+3)^2. Actually, even more elegant would be (2n+1)^2-(2n-1)^2 - can you see why?
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