Maths.. - Topic

Member

Posts: 12,207

Joined: Mar 4 2006

Gold: 4,360.00

Jan 10 2019 07:28pm

Quote (xaz @ Jan 8 2019 09:42am)

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 :(

X^2+bx+c = (x+n)*(x+m) where n+m=b and n*m=c
= x^2 +n+m+n*m
B= -5
C= 6

N=-2
M=-3
Is only viable answer

Edit all you guys on opposite page were missing -b in quadratic formula fyi

This post was edited by Xx Shin3d0wn xX on Jan 10 2019 07:30pm

feanur

Member

Posts: 16,662

Joined: Nov 24 2007

Gold: 15,245.00

Trader: Trusted

#12

Jan 11 2019 03:25am

Quote (Xx Shin3d0wn xX @ Jan 11 2019 02:28am)

(...)

N=-2
M=-3

(...)

That's correct.

And roots of X² - 5X + 6 are :
-N = 2
-M = 3

as said previously.

Cozzi

Banned

Posts: 14,020

Joined: Sep 23 2014

Gold: 101.00

#13

Jan 11 2019 09:09am

Simplify.... ?

kasey21

Member

Posts: 11,153

Joined: Aug 23 2008

Gold: 4,230.00

#14

Jan 11 2019 10:10am

Quote (xaz @ Jan 11 2019 05:09pm)

https://i.gyazo.com/6f2cb6d5631ccc08446ecad7946382f0.png

Simplify.... ?

On phone so not going to solve step by step but will show you what you use:
Perfect square formula:
(a+b)^2 = a^2 +2ab + b^2
5^x is a and 5^-x is b

The answer you should get is:
25^x + 2 + 25^-x

This post was edited by kasey21 on Jan 11 2019 10:12am

Xx Shin3d0wn xX

Member

Posts: 12,207

Joined: Mar 4 2006

Gold: 4,360.00

#15

Jan 12 2019 02:19pm

Quote (xaz @ Jan 11 2019 10:09am)

https://i.gyazo.com/6f2cb6d5631ccc08446ecad7946382f0.png

Simplify.... ?

(5^x+5^-x)^2
= (5^x+5^-x) * (5^x+5^-x)
= 5^(x+x)+5^x*5^-x+5^-x*5^x+5^(-x+-x)
=5^(2x) + 25^(x-x) + 25^(x-x) + 5^(-2x)
= 5^(2x) +1+1+ 5^(-2x)
=5^(2x) +2 + 5^(-2x)

Cozzi

Banned

Posts: 14,020

Joined: Sep 23 2014

Gold: 101.00

#16

Jan 15 2019 04:14am

Next one, can someone please solve this, I really can't make it happen.

(x-3)^2 - x^2 = x - 19

Supposedly, this is the answer but I don't understand what has been done to achieve this

x^2 - 6x + 9 - x^2 = x - 19

-6x + 9 = x - 19

9 = 7x - 19

28 = 7x

x = 4

The bolded part, I don't see how they got these numbers, someone please do explain. Thanks in advance!

EDIT//
I got it, nvm.. I feel stupid now. I forgot some of the basic rules hence not being able to solve it correctly, my bad.

This post was edited by xaz on Jan 15 2019 04:30am

Cozzi

Banned

Posts: 14,020

Joined: Sep 23 2014

Gold: 101.00

#17

Jan 15 2019 04:45am

Problem: 3x+2=5x-3

So I understand that I need to put 5x to the left side of the equation and +2 on the right side of the equation with different term but that's about it.

If I do that, wouldn't I get 3x-5x=-3-2?

In that caase -2x=-3-2 = -5

x = 5/2 (2.5)? is that correct or not how I did it?

This post was edited by xaz on Jan 15 2019 04:48am

kasey21

Member

Posts: 11,153

Joined: Aug 23 2008

Gold: 4,230.00

#18

Jan 15 2019 11:52am

That's right.

Cozzi

Banned

Posts: 14,020

Joined: Sep 23 2014

Gold: 101.00

#19

Jan 16 2019 05:02am

Really need help with this one:
(y+2)(y+7)=y^2+6y+20

I understand that I need to do y*y+y*7+2*y+2*7 and that's
y2+7y+2y+14=y^2+6y+20 but what about now? brainfreeze.. :wacko:

so the y^2s take eachother out and were left with
7y+2y+14=6y=20

9y+14=6y=20

what's the last step I need to take? where yall maths geniouses at? i'm certainly not one of them aha

This post was edited by xaz on Jan 16 2019 05:30am

otay

Member

Posts: 3,401

Joined: Feb 7 2011

Gold: 8,195.00

#20

Jan 16 2019 08:09am

Quote (xaz @ Jan 16 2019 05:02am)

Really need help with this one:
(y+2)(y+7)=y^2+6y+20

I understand that I need to do y*y+y*7+2*y+2*7 and that's
y2+7y+2y+14=y^2+6y+20 but what about now? brainfreeze.. :wacko:

so the y^2s take eachother out and were left with
7y+2y+14=6y=20

9y+14=6y=20

what's the last step I need to take? where yall maths geniouses at? i'm certainly not one of them aha

subtract 6y from both sides, subtract 14 from both sides

youre just trying to isolate y = something

Go Back To Homework Help Topic List