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Jan 8 2019 08:42am
Equation: x^2-5x+6=0

It was a while ago, but I need to get back at it again so here is my sheet.

Using what is called PQ-formula in Swedish (x^2+px+q=0)

So here is what I got

p=-5
q=6

x=5/2 +- sq root of (5/2^2) -6

x= 2.5 +- 2.5^2 -6

x= 2.5 +- 6.25 - 6

x= 2.5 +- .25

x1 = 2.75
x2 = 2.25

BUT the answer is supposted to somehow be:

x1= 2
x2= 3

Please someone highlight where I went wrong and show me how I can fix it. It's really been a while and I feel like I lost everything :(
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Jan 8 2019 09:24am
Idk what a pq switch is but it looks like you attempted to use the quadratic formula. This is fine but you are forgetting parts of it in the numerator we should have

-b +- sqrt(b^2 -4ac)


It would appear you’re missing parts of this.

Go to mathisfun and look at their quadratic formula example as a guide
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Jan 8 2019 11:37am
Quote (brigadier @ Jan 8 2019 05:24pm)
Idk what a pq switch is but it looks like you attempted to use the quadratic formula. This is fine but you are forgetting parts of it in the numerator we should have

-b +- sqrt(b^2 -4ac)


It would appear you’re missing parts of this.

Go to mathisfun and look at their quadratic formula example as a guide


Ok I think I got it now, please make sure I did it right :D

x^2-5x+6=0
x=5+-sqrt 5^2-4*1*6/2*1 (used the Quadratic Formula from here: https://www.mathsisfun.com/algebra/quadratic-equation.html)

x=5+-1/2

x1 = 3
x2 = 2

wohoo :banana: surely that's how it works right?
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Jan 8 2019 11:43am
Brings me to my next problem which is:

I know that to solve "v" out of s=v*t I need to isolate v on the right side of the equation first so I remove t from there by dividing v*t/t and doing the same on the left side s/t
That leaves me with s/t=v

So v= s/t

But what about this one:

Solve V out of p=m/v?, it's supposed to be V=m/p but I can't figure out how to do it when it's put like that
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Jan 8 2019 12:03pm
Quote (xaz @ Jan 8 2019 09:37am)
Ok I think I got it now, please make sure I did it right :D

x^2-5x+6=0
x=5+-sqrt 5^2-4*1*6/2*1 (used the Quadratic Formula from here: https://www.mathsisfun.com/algebra/quadratic-equation.html)

x=5+-1/2

x1 = 3
x2 = 2

wohoo :banana: surely that's how it works right?



Yeah just watch the order of operations

Common mistakes occur when trying to divide before using the square root

As for the pq switch thing I believe you are confusing factoring and the quadratic formula. I used to teach out of a textbook that had something similar to the p q switch you were talking about.
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Jan 8 2019 12:04pm
Quote (brigadier @ Jan 8 2019 08:03pm)
Yeah just watch the order of operations

Common mistakes occur when trying to divide before using the square root

As for the pq switch thing I believe you are confusing factoring and the quadratic formula. I used to teach out of a textbook that had something similar to the p q switch you were talking about.


But I solved it correctly in this post right?

Yeah I'm going to be more careful moving on and really take my time on it to not do wrong!

I was confusing factoring and quadratic formula, my excuse is that it's been a while but I'm trying my best to get back to it :D
Member
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Jan 8 2019 12:08pm
Quote (xaz @ Jan 8 2019 09:43am)
Brings me to my next problem which is:

I know that to solve "v" out of s=v*t I need to isolate v on the right side of the equation first so I remove t from there by dividing v*t/t and doing the same on the left side s/t
That leaves me with s/t=v

So v= s/t

But what about this one:

Solve V out of p=m/v?, it's supposed to be V=m/p but I can't figure out how to do it when it's put like that



S=vt

We see multiplication before the v and the t. You undid this operation by dividing (this is inverse operations).

P=m/v

We see m being divided by v. We need to undo division so we use the inverse operation to multiply both sides by v

P*v= (m/v)*v

P*v=mv/v

P*v=m


Now we see multiplication between the p and the v. We need to use the inverse operation and divide both sides by p.

(P*v)/p=m/p

V=m/p

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Jan 8 2019 12:11pm
Quote (xaz @ Jan 8 2019 10:04am)
But I solved it correctly in this post right?

Yeah I'm going to be more careful moving on and really take my time on it to not do wrong!

I was confusing factoring and quadratic formula, my excuse is that it's been a while but I'm trying my best to get back to it :D



I was just pointing out that eventually you will be asked to write the quadratic in factored form. That’s when you can think pq switch. Factoring will be immensely more useful down the road. Factor whenever possible.

It seemed right in your post.
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Jan 8 2019 12:14pm
Quote (brigadier @ Jan 8 2019 08:08pm)
S=vt

We see multiplication before the v and the t. You undid this operation by dividing (this is inverse operations).

P=m/v

We see m being divided by v. We need to undo division so we use the inverse operation to multiply both sides by v

P*v= (m/v)*v

P*v=mv/v

P*v=m


Now we see multiplication between the p and the v. We need to use the inverse operation and divide both sides by p.

(P*v)/p=m/p

V=m/p


Thanks a lot!
I will probably do some more posts here whenever I feel like it's needed. Sorry if you feel it is too easy, gotta start somewhere I guess
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Jan 8 2019 02:29pm
Post when you have questions. Someone will answer.
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