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Latif

Member

From: The Netherlands

Joined: 2015-03-13

Posts: 1,206

pls HELp with maths

I'm making an EE bot and I need HELp because I suck at maths. So I need someone who's good at maths.

I have:
y = x * 25 + (x * 25) ^ 2

and I want it inverted:
x = ...

HELp is much appreciated.

Gosha

Member

From: Russia

Joined: 2015-03-15

Posts: 6,206

Re: pls HELp with maths

It's a quadratic equation, there are 2 answers for x with every input of y

let z = (x * 25)
y = z + z^2
z^2 + z - y = 0
z = (-1 ± √(1 + 4y))/2
You'll get 2 answers for the z
z1 =  (-1 + √(1 + 4y))/2
z2 =  (-1 - √(1 + 4y))/2

then for each z find x

x = z/25

Edit: please note that if y = -¼ there will be only 1 answer because
± √0  is the same value for + and -

Also note that if y < -¼ you'll get negative value and you can't √ the negative value

So be sure to add some checks

Ruben101

Member

From: The Netherlands, not Holland

Joined: 2015-02-18

Posts: 78

Re: pls HELp with maths

It's a quadratic equation, there are 2 answers for x with every input of y

let z = (x * 25)
y = z + z^2
z^2 + z - y = 0
z = (-1 ± √(1 + 4y))/2
You'll get 2 answers for the z
z1 =  (-1 + √(1 + 4y))/2
z2 =  (-1 - √(1 + 4y))/2

then for each z find x

x = z/25

what did i just read xD

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Gosha

Member

From: Russia

Joined: 2015-03-15

Posts: 6,206

Re: pls HELp with maths

what did i just read xD

Standard formula for quadratic equation

ax^2 + bx + c = 0

D = b^2 + 4ac

x = -b ± √D
          2a

LukeM

Member

From: England

Joined: 2016-06-03

Posts: 3,009

Website

Re: pls HELp with maths

What are you using it for? :O

Any bot that requires actual maths gets bonus points from me

Firecrackericebreak

Member

Joined: 2015-02-15

Posts: 616

Re: pls HELp with maths

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625
y = x^2 + 75x + 625

y = ax^2 + bx + c

in this case:

a = 1
b = 75
c = 625

substitute these in for the quadratic formula which is as follows:

x = (-b ± √( ̅b^2 - 4ac )) / 2a
x = (-75 ± √(75^2 - 4(1)(625)) / 2(1)

and there is your x equals

if you want it even more simplified (after solving the equation):

x = -9.54915028125263 or -65.45084971874738

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LukeM

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From: England

Joined: 2016-06-03

Posts: 3,009

Website

Re: pls HELp with maths

▼Firecrackericebreak wrote:

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625
y = x^2 + 75x + 625

y = ax^2 + bx + c

in this case:

a = 1
b = 75
c = 625

substitute these in for the quadratic formula which is as follows:

x = (-b ± √( ̅b^2 - 4ac )) / 2a
x = (-75 ± √(75^2 - 4(1)(625)) / 2(1)

and there is your x equals

if you want it even more simplified (after solving the equation):

x = -9.54915028125263 or -65.45084971874738

You forgot about the y (to use the quadratic equation you need the other side to = 0), so you've only found the answer for y = 0

(I'm pretty sure Gosha's answer is correct though)

Edit: Oh wait, I didnt notice it was * not + as well (wasnt just you XD)

Zumza

Member

From: root

Joined: 2015-02-17

Posts: 4,645

Re: pls HELp with maths

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625

You must be American

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TaskManager

Formerly maxi123

From: i really should update this

Joined: 2015-03-01

Posts: 9,463

Re: pls HELp with maths

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625

You must be American

i dont get this meme HELp

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Bimps

Member

Joined: 2015-02-08

Posts: 5,067

Re: pls HELp with maths

so im gonna rewrite the equation as
y=(25x)^2+(25x)
because it is easier on my eyes
then i simplify and idk if im right
y-25x=(25x)^2
sqrt(y-25x)=25x
(sqrt(y-25x))/25=x
(sqrt(y-x))=x

so x=(sqrt(y-x)) is maybe the right answer. you probably was x on one side and maybe ill try it later but right now idek if this is right but yeah ok

on another note

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625

You must be American

why do u say that

EDIT: if i use my quadratic program i get
y=(x+1)x
so
y=x^2+x
y-x=x^2
sqrt(y-x))=x
holy **** i actually did it right.... wow. yeet

EDIT2:

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625

(25x)^2 != x^2 +50x +625. you thought of it as x + 25, but it isnt. therefore your entire post is for y=25x + (x +25)^2. those insane answers probably wouldnt with an equation as simple as this soo yeah

LukeM

Member

From: England

Joined: 2016-06-03

Posts: 3,009

Website

Re: pls HELp with maths

those insane answers probably wouldnt with an equation as simple as this soo yeah

Youd be surprised how unlikely getting nice numbers is in the real world when you have an x^2 (exams etc use numbers specifically chosen becuase they use nice results)

Bimps

Member

Joined: 2015-02-08

Posts: 5,067

Re: pls HELp with maths

those insane answers probably wouldnt with an equation as simple as this soo yeah

Youd be surprised how unlikely getting nice numbers is in the real world when you have an x^2 (exams etc use numbers specifically chosen becuase they use nice results)

yeah im aware but when a quadratic has a = 25, b = 25, and c = 0 the results arent gonna be...whatever that was

EDIT: also firebreaker, you used the quadratic equation wrong. it shouldve been y=, not x= . y = those two numbers. then you can factor it back in and simplify easier or whatever

EDIT: after consulting wolfram alpha, the equation is only true with the 3 following integer pairs: (0,0) (1,2) and (2,6)
here is the image it spat out

EDIT: there's more solutions than those three

LukeM

Member

From: England

Joined: 2016-06-03

Posts: 3,009

Website

Re: pls HELp with maths

▼LukeM wrote:

those insane answers probably wouldnt with an equation as simple as this soo yeah

Youd be surprised how unlikely getting nice numbers is in the real world when you have an x^2 (exams etc use numbers specifically chosen becuase they use nice results)

yeah im aware but when a quadratic has a = 25, b = 25, and c = 0 the results arent gonna be...whatever that was

EDIT: also firebreaker, you used the quadratic equation wrong. it shouldve been y=, not x= . y = those two numbers. then you can factor it back in and simplify easier or whatever

It was c = -y not c = 0, so you cant just get two numbers (and for the majority of cases it wont give a nice answer)

(and they needed to move the y to the right hand side, not put the quadratic equation equal to y, its specifically to find the variable used in the expression, not the expression's value)

Bimps

Member

Joined: 2015-02-08

Posts: 5,067

Re: pls HELp with maths

▼LukeM wrote:

those insane answers probably wouldnt with an equation as simple as this soo yeah

Youd be surprised how unlikely getting nice numbers is in the real world when you have an x^2 (exams etc use numbers specifically chosen becuase they use nice results)

yeah im aware but when a quadratic has a = 25, b = 25, and c = 0 the results arent gonna be...whatever that was

EDIT: also firebreaker, you used the quadratic equation wrong. it shouldve been y=, not x= . y = those two numbers. then you can factor it back in and simplify easier or whatever

It was c = -y not c = 0, so you cant just get two numbers (and for the majority of cases it wont give a nice answer)

(and they needed to move the y to the right hand side, not put the quadratic equation equal to y, its specifically to find the variable used in the expression, not the expression's value)

****

i thought 25x^2 was 25(x^2)
the x-intercepts are actually -1/25 and 0
so
y=(25x+1)x
y/(25x+1)=x
is that right

**** this

TaskManager

Formerly maxi123

From: i really should update this

Joined: 2015-03-01

Posts: 9,463

Re: pls HELp with maths

why are you all people resolving that equation smh gosha did it already
i guess ill hop on the bandwagon

y = x * 25 + (x * 25) ^ 2
y = 25(x + 25x^2)
x + 25x^2 = y/25
25x^2 + x - y/25 = 0
D = 1 - 4 * 25 * (-y/25) = 1 + 4y;
1 + 4y = 0 --> if y=-1/4 then there is one real value for X;
1 + 4y > 0 --> if y > -1/4 then there are two real values for X;
if y < -1/4 then the X1 and X2 are complex values;
X1 = (-1 - sqrt(D))/ 50
X2 = (-1 + sqrt(D))/ 50
where D = 1 + 4y

final result:
X1 = (-1 - sqrt(1+4y))/50
X2 = (-1 + sqrt(1+4y))/50

(checked the result with desmos, it does match)

Also note that if y < -1 you'll get negative value and you can't √ the negative value

incorrect. the critical point is y = -1/4 because you're taking sqrt(1+4y)

Edit: my bad, forgot a pair of brackets in the final result

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Abelysk

Guest

Re: pls HELp with maths

This thread is giving me PTSD from the F grade I got

Latif

Member

From: The Netherlands

Joined: 2015-03-13

Posts: 1,206

Re: pls HELp with maths

Thanks for the HELp guys

EDIT: @LukeM this is not for an EE bot I thought I would make it for EE lol.

Anatoly

Guest

Re: pls HELp with maths

▼Forget this.

y = x * 25 + (x * 25) ^ 2

I'm making an EE bot and I need HELp because I suck at maths. So I need someone who's good at maths.

I have:
y = x * 25 + (x * 25) ^ 2

and I want it inverted:
x = ...

HELp is much appreciated.

You all missed one point! "=" is the set operator, not an "equal" operatorion:

y=x*25+(x*25)²

x*25+(x*25)² = x*25 + x * 25 * x *25 = 25x(1+25x)

https://www.kontrolnaya-rabota.ru/s/equ … =-10&b0=10
https://www.kontrolnaya-rabota.ru/s/equ … =-10&b0=10

TaskManager

Formerly maxi123

From: i really should update this

Joined: 2015-03-01

Posts: 9,463

Re: pls HELp with maths

▼Forget this.

y = x * 25 + (x * 25) ^ 2

I'm making an EE bot and I need HELp because I suck at maths. So I need someone who's good at maths.

I have:
y = x * 25 + (x * 25) ^ 2

and I want it inverted:
x = ...

HELp is much appreciated.

You all missed one point! "=" is the set operator, not an "equal" operatorion:

y=x*25+(x*25)²

x*25+(x*25)² = x*25 + x * 25 * x *25 = 25x(1+25x)

https://www.kontrolnaya-rabota.ru/s/equ … =-10&b0=10
https://www.kontrolnaya-rabota.ru/s/equ … =-10&b0=10

you ain't tricking us with these russian spying links!

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Anatoly

Guest

Re: pls HELp with maths

you ain't tricking us with these Russian spying links!

But I'm too young for a spy. Also if I'd spy, then definitely not you!

TaskManager

Formerly maxi123

From: i really should update this

Joined: 2015-03-01

Posts: 9,463

Re: pls HELp with maths

you ain't tricking us with these Russian spying links!

But I'm too young for a spy. Also if I'd spy, then definitely not you!

well obviously because you already got caught

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Anatoly

Guest

Re: pls HELp with maths

▼maxi123 wrote:

you ain't tricking us with these Russian spying links!

But I'm too young for a spy. Also if I'd spy, then definitely not you!

well obviously because you already got caught

Can only say: President Medvedev

kreacher

Member

From: Wakanda

Joined: 2015-03-31

Posts: 409

Re: pls HELp with maths

nice a challenge ill try

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Est. December 2010

kreacher

Member

From: Wakanda

Joined: 2015-03-31

Posts: 409

Re: pls HELp with maths

y = x * 25 + (x * 25) ^ 2
y = x * 25 + x^2 + 50x + 625

um (x*25)(x*25)=x^2+625 its not (x+25)(x+25) so u dont times them all by each other

is this right? y=25x+625x^2
625x^2+25x=0
(-25+(625-2500))/1250=-1.52
(-25-(625-2500))/1250=0.74

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Est. December 2010

LukeM

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From: England

Joined: 2016-06-03

Posts: 3,009

Website

Re: pls HELp with maths

y=25x+625x^2
625x^2+25x=0

AAAHHHHH!!!!! WHY DOES EVERYONE FORGET ABOUT THE y?????
625x^2 + 25x - y=0

other than that I think its correct though

(also I'm pretty sure Gosha's answer is correct, so use that to check)