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# completing the square watch

1. x^2 - 3x + 5 in the form (x - p)^2 + q
can anyone plx explain how do i do completing the square because i dont know if there is a method to do them
i suck at maths lol
2. (Original post by coolmathametics)
x^2 - 3x + 5 in the form (x - p)^2 + q
can anyone plx explain how do i do completing the square because i dont know if there is a method to do them
i suck at maths lol
3. (Original post by DylanJ42)
oml that looks way confusing lol
would u be able to make up an example n substitute the values plx so that way i know what to substitute n what is actually happening
4. (Original post by coolmathametics)
x^2 - 3x + 5 in the form (x - p)^2 + q
can anyone plx explain how do i do completing the square because i dont know if there is a method to do them
i suck at maths lol
I recommend you watch a few videos on the topic and then come back to us if you're still stuck. You could try this video for example.
5. (Original post by DylanJ42)
Is that really going to help someone who can't complete the square for simple quadratic expressions?
6. (Original post by coolmathametics)
oml that looks way confusing lol
would u be able to make up an example n substitute the values plx so that way i know what to substitute n what is actually happening
yea sure, so something like

to complete the square we write this as

this is because if you multiply out the squared bracket you get , however we only want so we need to subtract the 4
7. (Original post by notnek)
I recommend you watch a few videos on the topic and then come back to us if you're still stuck. You could try this video for example.
i can do those ones but if the middle term is 7 or 11 then its a bit difficult

(Original post by notnek)
Is that really going to help someone who can't complete the square for simple quadratic expressions?
lol i did i say i suck at maths but not that much, i can do simple ones but difficulty with the ones i explained above
8. (Original post by DylanJ42)
yea sure, so something like

to complete the square we write this as

this is because if you multiply out the squared bracket you get , however we only want so we need to subtract the 4
what is the middle term is 11 instead
9. (Original post by coolmathametics)
what is the middle term is 11 instead
are you comfortable with the idea of comparing coefficients

eg if then a=3 and b=4

does that make sense?
10. can some1 help me plx
sorry if i seems desperate
11. (Original post by coolmathametics)
i can do those ones but if the middle term is 7 or 11 then its a bit difficult
You should have mentioned that in your initial post

Can you try completing the square for x^2 - 3x + 5?

It will be useful if you show us where you get stuck so please post all your working / thoughts up to the point you get stuck.

Also, is this for A Level or GCSE? Will you be using a calculator to do these types of questions?
12. (Original post by coolmathametics)
can some1 help me plx
sorry if i seems desperate
If you have then it can be written in the form

So in your question you have and - all it means is that an odd number being halved will give you a fraction to work with instead.

To understand why this works, you should watch a video on it and see how this is derived.
13. (Original post by notnek)
You should have mentioned that in your initial post

Can you try completing the square for x^2 - 3x + 5?

It will be useful if you show us where you get stuck so please post all your working / thoughts up to the point you get stuck.

Also, is this for A Level or GCSE? Will you be using a calculator to do these types of questions?
ooops sorry but i can do e.g. x^2 + 4x + 6
because i k 2 + 2 would be 4
so its gonna be (x+2)^2 + 2 i think :/
regards to ur question, i dunno how to start like the first step cox i can't find the half of 3x so its gonna be like 3/2 which is gonna be difficult to see how to work out the part that goes outside of the bracket... if u see what i mean

its for A level - core 1 non cal
14. (Original post by DylanJ42)
are you comfortable with the idea of comparing coefficients

eg if then a=3 and b=4

does that make sense?
i am so confused
ok so lets say ---> x^2 + 7x - 3
what i need to know is how i get half of 7 cox it cant be divided by 2
15. (Original post by coolmathametics)
x^2 - 3x + 5 in the form (x - p)^2 + q
can anyone plx explain how do i do completing the square because i dont know if there is a method to do them
i suck at maths lol
http://www.mathsgenie.co.uk/completing-the-square.html
Watch this ^ the guy explains it quickly and easily.
16. (Original post by coolmathametics)
i am so confused
ok so lets say ---> x^2 + 7x - 3
what i need to know is how i get half of 7 cox it cant be divided by 2
its just , fractions are allowed in completing the square
17. (Original post by DylanJ42)
its just , fractions are allowed in completing the square
alright but how am i gonna work out + q (the outside bit)
18. (Original post by Anonymous1502)
http://www.mathsgenie.co.uk/completing-the-square.html
Watch this ^ the guy explains it quickly and easily.
i can do those ones pretty easily cox there ain't any fractions in the answer *_*
19. (Original post by coolmathametics)
ooops sorry but i can do e.g. x^2 + 4x + 6
because i k 2 + 2 would be 4
so its gonna be (x+2)^2 + 2 i think :/
regards to ur question, i dunno how to start like the first step cox i can't find the half of 3x so its gonna be like 3/2 which is gonna be difficult to see how to work out the part that goes outside of the bracket... if u see what i mean

its for A level - core 1 non cal
There are different ways to think about 'completing the square' but I recommend this method when there are fractions and it's non calculator:

E.g.

Start by halving to get as you say

So you get

Then you need to subtract the square of and then add on 5 (let me know if you can't see where I'm getting these numbers from).

So you end up with :

Now change the so it has the same denominator as

Now see if you can follow this process for a different example. Post your working if you get stuck.
20. (Original post by coolmathametics)
alright but how am i gonna work out + q (the outside bit)
as notnek said, try do an example so we can see where you get stuck.

try complete the square on

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