Math quadratic equation

[c0d0ps]

Second grade equation, PQ formula: Solve following equations

x^2-x-20=0

Solve variable: X

 

Dafuq am I supposed to do with this one ..?

 

Edit: My math teacher has already helped me with this and therefor I will stop follow this thread.

It seems like I didn't put enough empathize on the PQ formula on this start comment I think this is why I didn't get the answers I was looking for and instead raised some confusions. But now it's all worked out, so thank you all for your help.

 

 

Answer: x^2-x-20=0 <=> x=0,5 +- sqrt 0,5^2 + 20 <=> x= 0,5 +- sqrt 20,25 <=> x= 0,5 +- 4,5

[FireFox]

No idea, I used to be able to do basic equasions years ago at school but I have nothing on that, maybe I'm stupid

[c0d0ps]

No idea, I used to be able to do basic equations years ago at school but I have nothing on that, maybe I'm stupid

I can do the previous ones and some after it but this one I don't get

[hazza_ob]

x = -b plus or minus the square root of: b [squared] time 4 times a times c all over 2a

ax[sqaured] + bx + c

 

 

 

http://goo.gl/y7hx05

[c0d0ps]

x = -b plus or minus the square root of: b [squared] time 4 times a times c all over 2a

ax[sqaured] + bx + c

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

[Nineshadow]

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

 

Quadratics are so damn easy.

Use the formula.

 

Or, if you want to do it by factorizing :

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

 something times something is 0 if either one of them is 0.

So x1 = -4 (-4 + 4 = 0) and x2 = 5 (5 - 5 = 0)

 

You need to divide the middle term into two others that multiplied are equal to the third one.

[Timopomer]

x² - x - 20 = (x - 5)(x + 4) = 0

 

for x to be 0 in one case

 

x1 = 5

 

in the other

 

x2 = -4

[SIGSEGV]

a=1 because there is nothing in front of the X^2 which is the same as 1X^2

b=1 because there is nothing in front of the other X which is the same as 1X

c=-20 because it ends in -20

Then just put them into quadratic formula

[1funnygame]

https://answers.yahoo.com/question/index?qid=20100319142854AA8o9O7

[Hans Christian | Teri]

Dafuq am I supposed to do with this one ..?

 

Solve it?

[c0d0ps]

x² - x - 20 = (x - 5)(x + 4) = 0

 

for x to be 0 in one case

 

x1 = 5

 

in the other

 

x2 = -4

Where do you get  "(x - 5)(x + 4)" from? Is it rearranged or something?

[hazza_ob]

google the quadratic formula, it'll help you when you're stuck like this but yeah that guy ^ has got the answer

[Timopomer]

Solve it?

teri the know-all guy 

[Nup]

if you cant factorise use the -b formula mentioned. 

[Arphenyte]

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

 

You need to find a number that multiplied gives -20 and sustracted gives 1. Thus your x=5, x=-4.

5-4=1.

[c0d0ps]

Solve it?

Yes, but how?

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

[Nup]

Where do you get  "(x - 5)(x + 4)" from? Is it rearranged or something?

it's factorised. Somewhat tricky to get the hang of imo, but very very important. Look it up on khan academy  

[c0d0ps]

https://answers.yahoo.com/question/index?qid=20100319142854AA8o9O7

I have already seen that one. It doesn't help me one bit, I don't understand anything there.

[c0d0ps]

Quadratics are so damn easy.

Use the formula.

 

Or, if you want to do it by factorizing :

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

 something times something is 0 if either one of them is 0.

So x1 = -4 (-4 + 4 = 0) and x2 = 5 (5 - 5 = 0)

 

You need to divide the middle term into two others that multiplied are equal to the third one.

"x(x+4) - 5(x+4" Where do you get this from, how?

[Timopomer]

Where do you get  "(x - 5)(x + 4)" from? Is it rearranged or something?

 

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

[c0d0ps]

google the quadratic formula, it'll help you when you're stuck like this but yeah that guy ^ has got the answer

I have tried but it doesn't help me.

I get something like x= -x/2 square root of (x/2)^2 + 20

Then I don't know what to do.

[FireFox]

Solve it?

 

Straight to the point, I love it lol

[Nineshadow]

"x(x+4) - 5(x+4" Where do you get this from, how?

You factorize???

 

x^2 + 4x = x(x + 4)

[Arphenyte]

Yes, but how?

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

x^2-x-20=0

You need to find 2 numbers that multiplied gives you the third term which is -20.

But also need to gives 1 which is your second term.

 

And so the only numbers that can do that are 5, and -4. You can apply that logic to any quadratic equation.

[c0d0ps]

You need to find a number that multiplied gives -20 and sustracted gives 1. Thus your x=5, x=-4.

5-4=1.

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.