Math quadratic equation

[c0d0ps]

yes.

 

x*x - 5*x + 4*x - 20

 

x^2 -x - 20

 

if you dont know how to solve it when you see the solution like this i think you should look into this

 

http://en.wikipedia.org/wiki/Quadratic_equation

 

this is how most equations are solved. from easy ones like yours to complicated ones with Squared Cos functions everything works

I have already tried to use it. But I can't complete it. (For this equation, most other I can do)

[Si3Rra_7]

Wow these are soo easy , i wish i was still at those and not fukin about with derivatives and integrals

[Arphenyte]

I am supposed to be able to complete this one with the PQ formula I think. Or the quad something formula that it might be called in English.

You don't need it in this case... but if really need to apply it, you should watch some videos about it on youtube.

[Arphenyte]

Wow these are soo easy , i wish i was still at those and not fukin about with derivatives and integrals

Ez.

[SirRoderick]

The answers are x=5 and x= -4 I just don't know how to get there.

Btw, I have no idea what you just said

Does the term "Determinants" mean anything to you? Cause that's what you need to use

[c0d0ps]

Wow these are soo easy , i wish i was still at those and not fukin about with derivatives and integrals

Well, if you are used to it then I am pretty sure it's the same difficulty .. (If you work up for it and not just start there)

Example: If you have never done something before like ride a bike, it will be really difficult but after you practice for a while it's incredibly easy.

[c0d0ps]

Does the term "Determinants" mean anything to you? Cause that's what you need to use

No.

I do math in Swedish.

[Timopomer]

 

1 +- squareroot( (-1)^2 - 4*1*-20)

----------------------------------------------

                           2

 

 

1 +- squareroot( 1 + 80)

----------------------------------------------

                           2

 

 

1 +- 9

---------

   2

 

 

1-9         = -4

-----

 2

 

 

1+9         = 5

-----

 2

[SIGSEGV]

Yes, but how?

If I could solve it, then I wouldn't post it here.

a=1

b=1

c=-20

(-b±sqrt(b²-4ac))/2a

Now, substituted everything in

(-1±sqrt(1²-4*1*-20))/2*1

Begin simplifying

(-1±sqrt(1-4*-20))/2

Don't forget to do brackets then multiplication first

(-1±sqrt(1+80))/2

Add the one

(-1±sqrt(81))/2

Square root 81

(-1±9)/2

Then since we have ± get two answers, one for - and one for plus

(-1+9)/2=first answer

(-1-9)/2=second answer

Figure out the brackets

(8)/2=first answer

(-10)/2=second answer

Remove the brackets

8/2=first answer

-10/2=second answer

Divide by two

4=first answer

-5=second answer

So the answer is:

X= 4 or -5

[Nup]

You need to learn to factorise.

 

It's another way to get the roots, without using the -b method. Comes in very handy in other areas too. 

 

This is probably the easiest method 

[GrimNeo]

LinusMathTips

[Timopomer]

No.

I do math in Swedish.

look above.

 

 

a is what comes before the x^2

 

in x^2

a=1

 

b is what comes before the plain not squared x

 

in -x

b=-1

 

c is the number without an x in it

 

in -20

b=-20

 

x^2-x-20 = 0

[c0d0ps]

a=1

b=1

c=-20

(-b±sqrt(b²-4ac))/2a

Now, substituted everything in

(-1±sqrt(1²-4*1*-20))/2*1

Begin simplifying

(-1±sqrt(1-4*-20))/2

Don't forget to do brackets then multiplication first

(-1±sqrt(1+80))/2

Add the one

(-1±sqrt(81))/2

Square root 81

(-1±9)/2

Then since we have ± get two answers, one for - and one for plus

(-1+9)/2=first answer

(-1-9)/2=second answer

Figure out the brackets

(8)/2=first answer

(-10)/2=second answer

Remove the brackets

8/2=first answer

-10/2=second answer

Divide by two

4=first answer

-5=second answer

So the answer is:

X= 4 or -5

Note: It's easier for me to follow you if you use the same variable as in the equation I am trying to solve.

[c0d0ps]

You need to learn to factorise.

I know how to factorize but I am supposed to learn how to use PQ formula aka quad something formula. 

In this part of the book.

[c0d0ps]

look above.

 

 

a is what comes before the x^2

 

in x^2

a=1

 

b is what comes before the plain not squared x

 

in -x

b=-1

 

c is the number without an x in it

 

in -20

b=-20

 

x^2-x-20 = 0

I still don't understand ..

I'll try a little bit more then come back.

[c0d0ps]

LinusMathTips

I would use linustechtips for everything if I could .. 

[Si3Rra_7]

Well, if you are used to it then I am pretty sure it's the same difficulty .. (If you work up for it and not just start there)

Example: If you have never done something before like ride a bike, it will be really difficult but after you practice for a while it's incredibly easy.

i know but they were easy when i learned , i just have a match proficiency that comes with a GREAT maternal language deficiency ( can't do essays for shit )

[Nup]

I know how to factorize but I am supposed to learn how to use PQ formula aka quad something formula. 

In this part of the book.

Ahh i see, my appologies. The formula is v. handy it follow the structure of the exuation which is ax^n+bx+c=0 and use the values which line up with the constants (letters) in the equation given, -b eqn  

[c0d0ps]

Ahh i see, my appologies. The formula is v. handy it follow the structure of the exuation which is ax^n+bx+c=0 and use the values which line up with the constants (letters) in the equation given, -b eqn

The formula I've been taught is: x= - p/2 +- sqrt (p/2)^2 - q

I am not entirely sure if it's the same are you're talking about but it looks pretty similar.

[Nup]

The formula I've been taught is: x= - p/2 +- sqrt (p/2)^2 - q

I am not entirely sure if it's the same are you're talking about but it looks pretty similar.

Oh, i havent heard of that, i shall go learn about it!  

[c0d0ps]

Oh, i havent heard of that, i shall go learn about it!

I think it is Quad something formula in English but in Sweden we say PQ formula.

[GrimNeo]

I would use linustechtips for everything if I could .. 

I don't blame you. I have not done these in 8 years. I have never used these in the real world. I like learning them again. Math was my best subject.

[Toxic Tom]

The easiest method to use is called "split and group"

 

You do this:

 

First of all make sure your LHS (left hand side) is equal to zero, in this case, it is.

 

x^2-x-20=0

 

a=1 (coefficient of x^2)

b=-1 (coefficient of x)

c=-20

 

Find two numbers that add to make b, and multiply to make ac (in this case -5 and 4, because -5+4=-1=b and -5*4=-20=c [and seeing as a=1, ac=c])

 

Then split the b component of the equation into the two numbers found above (-5 and 4)

 

x^2-5x+4x-20=0

 

Then factorise x^2-5x and 4x-20 separately to make:

 

x(x-5)+4(x-5)=0

 

NOTE: Whatever is inside the brackets should be the same for both brackets, if it's not, you did it wrong.

 

To simplify the factorised equation into double brackets you put the x+4 (the bit outside the brackets of the previous equation) in the first bracket, and the x-5 (the bit inside the brackets of the previous equation) in the second bracket to make:

 

(x+4)(x-5)=0

 

Now, for this to be true, one of the brackets must equal zero.

 

So either x+4=0 or x-5=0

So x=-4 or x=5

[c0d0ps]

The easiest method to use is called "split and group"

 

You do this:

 

First of all make sure your LHS (left hand side) is equal to zero, in this case, it is.

 

x^2-x-20=0

 

a=1 (coefficient of x^2)

b=-1 (coefficient of x)

c=-20

 

Find two numbers that add to make b, and multiply to make ac (in this case -5 and 4, because -5+4=-1=b and -5*4=-20=c [and seeing as a=1, ac=c])

 

Then split the b component of the equation into the two numbers found above (-5 and 4)

 

x^2-5x+4x-20=0

 

Then factorise x^2-5x and 4x-20 separately to make:

 

x(x-5)+4(x-5)=0

 

NOTE: Whatever is inside the brackets should be the same for both brackets, if it's not, you did it wrong.

 

To simplify the factorised equation into double brackets you put the x+4 (the bit outside the brackets of the previous equation) in the first bracket, and the x-5 (the bit inside the brackets of the previous equation) in the second bracket to make:

 

(x+4)(x-5)=0

 

Now, for this to be true, one of the brackets must equal zero.

 

So either x+4=0 or x-5=0

So x=-4 or x=5

I don't completely understand it but it makes slightly more sense. I'll try to use it in the future if I remember.

 

"I don't blame you. I have not done these in 8 years. I have never used these in the real world. I like learning them again. Math was my best subject"-GrimNeo

"The above post was written to offend as many people as possible" - You

Ehm .. 

[Toxic Tom]

I don't completely understand it but it makes slightly more sense. I'll try to use it in the future if I remember.

 

Try it with some practice questions and you'll soon pick it up

 

"I don't blame you. I have not done these in 8 years. I have never used these in the real world. I like learning them again. Math was my best subject"-GrimNeo

"The above post was written to offend as many people as possible" - You

Ehm .. 

 

Not quite sure what you're insinuating there