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# Can't seem to be able to complete the square for this? watch

1. Part b) specifically.

I did 2x^2 + 8x + 3 = (x+2)^2 - 4 + (3/2)
= (x+2)^2 - (5/2)

That is apparently incorrect.
The answer is 2(x + 2)^2 - 5

I don't understand how that was achieved though. I see it like this:
2(x^2 +4x + (3/2))

2((x + 2)^2 - 4 + (3/2)), which is practically the same?
How else do I do this?

And can anyone explain to me why 2(x^2 +4x + (3/2)) is the same as just x^2 + 4x + (3/2) ? I mean surely they're not equal, the first one is x2 the second one, but I was taught that doing so to an equation is fine?
2. (Original post by frostyy)
...
Do you agree that you can write ? i.e: you can pull a factor of 2 out?

So for example, when you're given you can then pull the common factor of 2 out to get you .

Then you complete the square on the inside: .

Which step don't you understand in here?
3. Try arranging 2x^2 + 8x into p(x+q)^2

2(x+2)^2 which is equal to 2(x^2 + 4x + 4).

If you expand that it becomes 2x^2 + 8x + 8, then you have to find what r is equal to to make +8 equal to +3
4. (Original post by Zacken)
Do you agree that you can write ? i.e: you can pull a factor of 2 out?

So for example, when you're given you can then pull the common factor of 2 out to get you .

Then you complete the square on the inside: .

Which step don't you understand in here?
Oh right, sorry. I just left it in the form 2((x+2)^2 - (5/2)) and got confused.

Anyway, cheers, I really appreciate your help in all the topics that I post on this website, I really do. Hope Jesus will give you many women, you deserve them.
5. (Original post by frostyy)
Oh right, sorry. I just left it in the form 2((x+2)^2 - (5/2)) and got confused.

Anyway, cheers, I really appreciate your help in all the topics that I post on this website, I really do. Hope Jesus will give you many women, you deserve them.
Yay! Glad that cleared things up. Cheers, mate - don't worry about it.

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