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Any1 brainy out there? help pls!

ok so I've got this math question about algebra- completing the square...
i dont hav a clue how to answer it... help please?
Original post by #animal-lover
ok so I've got this math question about algebra- completing the square...
i dont hav a clue how to answer it... help please?


asd.PNG
here is the question....
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Original post by #animal-lover
asd.PNG
here is the question....


ok so the coefficient of x^2 is 1, meaning that we can use the general formula for completeting the square:

x^2 + ax + b = (x+a/2)^2 -(a/2)^2 + b

Then once u have that formula rearranged to the general formula, u can make it equal to 0 and solve it.
wen i saw u were looking for anyone brainy, i was thinking yep defo me, but bruv wat the f is that, is it some made up question or wat?

In other words cant help u b
And brainy isnt part of my resume or personality traits :biggrin:
Original post by AKA2234
bruv wat the f is that, is it some made up question or wat?

...it's the quadratic formula, goddammit!
dude i knew that, but i was done with maths last year, literally messed up my brain, forgot everything about it
Original post by brownguytorule
ok so the coefficient of x^2 is 1, meaning that we can use the general formula for completeting the square:

x^2 + ax + b = (x+a/2)^2 -(a/2)^2 + b

Then once u have that formula rearranged to the general formula, u can make it equal to 0 and solve it.


soo your saying x^2 = 1??
so is it gonna be (x+9)^2 + 4= 0???
if you are trying to complete the square for

y = x2 + 18x + 4

you can start off by dividing the 18 by 2 to get 9...

y = ( x + 9 )2 + ....

now think about 92 which is 81.

how can you reduce 81 down to 4 ?

minus 77....

so put it together

y = ( x + 9 )2 - 77

after that you have to solve

( x + 9 )2 - 77 = 0

which you can do yourself.
the formula for the quadratic equation is: ax^2+bx+c=0
in your case, a = 1 b = 18 c = 4
the formula for finding x is:
x1 = (-b + sqrt(b^2-4ac) ) / 2a
and
x2 = (-b - sqrt(b^2-4ac) ) / 2a
so the answers for that are:
x1 = (-18 + sqrt(18^2-4*1*4) ) / 2*1 = -9 + sqrt308
and
x2 = (-18 - sqrt(18^2-4*1*4) ) / 2*1 = -9 - sqrt308
cheers
Original post by the bear
if you are trying to complete the square for

y = x2 + 18x + 4

you can start off by dividing the 18 by 2 to get 9...

y = ( x + 9 )2 + ....

now think about 92 which is 81.

how can you reduce 81 down to 4 ?

minus 77....

so put it together

y = ( x + 9 )2 - 77

after that you have to solve

( x + 9 )2 - 77 = 0

which you can do yourself.


Ok so how abt the question: x2+ 12x + 4 = 0
Original post by #animal-lover
Ok so how abt the question: x2+ 12x + 4 = 0


12 divided by 2 = ?

?2 = ??

how do you get from ?? down to 4.... :hmmmm2:
Original post by #animal-lover
Ok so how abt the question: x2+ 12x + 4 = 0


the formula is already given above.

x1 = -6 + 0.5*sqrt128
x2 = -6- 0.5*sqrt128
Original post by the bear
12 divided by 2 = ?

?2 = ??

how do you get from ?? down to 4.... :hmmmm2:


12 divided by 2 is 6
so 62 = 36
so how do u get from 36 down to 4??
Original post by #animal-lover
12 divided by 2 is 6
so 62 = 36
so how do u get from 36 down to 4??


okay... what do you do ?
x2+ 12x + 4 = 0

x= ....... + √..... or x= ........ - √.......

that is the question on my paper- i have to give a postive and negative answer using that equation....
the ...... is a space that i have to fill in
hmmmmm
Original post by #animal-lover
x2+ 12x + 4 = 0

x= ....... + √..... or x= ........ - √.......

that is the question on my paper- i have to give a postive and negative answer using that equation....
the ...... is a space that i have to fill in
hmmmmm


x= -6 + √32 or x= -6 - √32
its better to google how to solve quadratic equations, mate

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