PDA

View Full Version : Solving Equations Algebraically?


peachesapples123
Feb 25, 2007, 10:33 PM
Can somebody please explain to me how to solve this algebraically to find the x-intercepts?

x squared - 5x = -6

Sorry, I forgot it. XP

tweeetypooh
Feb 25, 2007, 11:18 PM
Can somebody please explain to me how to solve this algebraically to find the x-intercepts?

x squared - 5x = -6

Sorry, I forgot it. XP
the answer is (x-2)(x-3)=0
thus the values of x are 2 and 3.

this is how it is done:
x^2 - 5x = -6
transpose
x^2 - 6x + 6 = 0
then factor it out
(x - 2)(x - 3) = 0 ; (-2) and (-3) when added will get (-5) which is the middle term
then equate both terms in zero:
(x - 2) = 0 and (x - 3) = 0
thus
x = 2 and x = 3.

those are the x-intercepts.

peachesapples123
Feb 25, 2007, 11:45 PM
the answer is (x-2)(x-3)=0
thus the values of x are 2 and 3.

this is how it is done:
x^2 - 5x = -6
transpose
x^2 - 6x + 6 = 0
then factor it out
(x - 2)(x - 3) = 0 ; (-2) and (-3) when added will get (-5) which is the middle term
then equate both terms in zero:
(x - 2) = 0 and (x - 3) = 0
thus
x = 2 and x = 3.

those are the x-intercepts.Thank you so much but I'm still confused. The teacher didn't even teach this to us yet. :confused: Thank you though.

cool_dude
Feb 26, 2007, 02:48 PM
I suggest waiting until the teacher teaches you this. However I believe that the teacher did teach you this and you just don't understand because you would not get this assigned if the teacher didn't teach it yet. Anyhow lets get back to your problem.

we need to solve for x. there are 2 ways to solve for x in your equation. Either use the quadratic formula or factor like tweetypooh showed.

if you can't solve for x in such a simple equation than I think you should go in for some extra help because tweetypooh explained very well how to solve for x. nothing more can be stated.

Edit: Exactly what don't you get about tweetypooh explanation?

peachesapples123
Feb 26, 2007, 05:39 PM
She did assign this to us, but we didn't learn it yet. It's in chapter 10 but we're still on chapter 9. I'm pretty sure the teacher didn't teach this to us because even when I ask my friends, they don't get it either. And they get these math things better than I do since they're straight A students and all.

No, I don't go in for extra help I just ask for help from friends. The reason I didn't get it is because it's over the computer. For me to learn how to do something, I need to see it and hear it, and see it done more than once. I need to also do it myself as the person does it.

What I didn't get about tweetypooh's explanation is if adding a negative really doesn't matter because they got 2 and 3 and according to the back of the book and my older brother, the answer is -2 and -3.

cool_dude
Feb 26, 2007, 08:54 PM
x = 2 and x = 3 is correct. I guess the answers in your book are wrong which happens all the time. I'm still surprised your teacher would assign something that has not been taught yet especially since your only in grade 9/10.

peachesapples123
Feb 27, 2007, 04:16 PM
Really? But my oldest brother got -2 and -3. He's in grade 12. She does do that sometimes though. My friends even want to send in a complaint because of that. I'm actually in grade 8.

cool_dude
Feb 27, 2007, 04:26 PM
I don't remember doing x intercepts in grade 8. its grade 9 work. I'm also in grade 12 math and I know that tweetypooh answer is correct. Post the solution that your brother has (the full solution all the steps) and I will tell you where he went wrong.

Edit: just noticed tweetypooh made typo. On second line he wrote x^2 - 6x + 6 = 0 but it should be x^2 - 5x + 6 = 0
anyhow he did all the work right he just made a typo. The answer is still the same.

peachesapples123
Feb 27, 2007, 10:22 PM
I didn't watch him do his work. He did it and told me that he got -2 and -3. Yeah, because I'm kind of in an advanced class. I'm in Algebra in grade 8 even though it's average to go into Algebra at grade 9. Or at least that's what I was told.

Oh, okay.

tweeetypooh
Feb 27, 2007, 11:18 PM
i don't remember doing x intercepts in grade 8. its grade 9 work. I'm also in grade 12 math and i know that tweetypooh answer is correct. Post the solution that your brother has (the full solution all the steps) and i will tell you where he went wrong.

Edit: just noticed tweetypooh made typo. on second line he wrote x^2 - 6x + 6 = 0 but it should be x^2 - 5x + 6 = 0
anyhow he did all the work right he just made a typo. the answer is still the same.

Thanks for correcting my typo... I was in a hurry when I did that... and by the way, I'm a "she."

tweeetypooh
Feb 27, 2007, 11:30 PM
She did assign this to us, but we didn't learn it yet. It's in chapter 10 but we're still on chapter 9. I'm pretty sure the teacher didn't teach this to us because even when I ask my friends, they don't get it either. And they get these math things better than I do since they're straight A students and all.

No, I don't go in for extra help I just ask for help from friends. The reason I didn't get it is because it's over the computer. For me to learn how to do something, I need to see it and hear it, and see it done more than once. I need to also do it myself as the person does it.

What I didn't get about tweetypooh's explanation is if adding a negative really doesn't matter because they got 2 and 3 and according to the back of the book and my older brother, the answer is -2 and -3.


I added (-2) and (-3) which resulted to (-5) which is the middle term. This process is not necessary though. It's done just to check and make sure you're on the right process.

maybe you're confused how the answer turned out to be -2 and -3 in your book. I think maybe what was wriiten there was: "x - 2 = 0 ; and x - 3 = 0"
but basically, if you really want to get the value of x, you really need to transpose it.
x - 2 = 0 is the same as x = 2 ; and x - 3 = 0 is the same as x = 3.

the basic rule when equating it to zero is to change positive to negative. Right?

I don't know why the answer on your book is -2 and -3.

tweeetypooh
Feb 27, 2007, 11:44 PM
if you really don't trust my answer, try checking the equation with the value you got.

for example, your equation is : x^2 - 5x = -6;
if you try to use my answer, which is 2 and 3, try substituting it to the eqn like this
if x = 2 then
2 squared - 5(2) = -6
4 - 10 = -6
-6 = -6... correct?? Right?;)
but if you insist your books answer, which is -2, look what will happen:
if x = -2 then
-2 squared - 5(-2) = -6
4 - (-10) = -6
14 = -6... very wrong... :o

AND

if x = 3 then
3 squared - 5(3) = -6
9 - 15 = -6
-6 = -6... correct again.. ;)
but if you really insist you books answer again,
if x = -3 then
-3 squared - 5(-3) = -6
9 - (-15) = -6
24 = -6... really wrong:o

not all books are perfectly made. There are still some errors on it. I was a student once and I used to copy the answers on the back for my homeworks. Turned out that some answers are really wrong... trust me kid... I am confident on my solution.. I am an engineer... :D :eek:

tweeetypooh
Feb 27, 2007, 11:54 PM
if your really don't trust my answer, try solving using cool_dudes suggestion. Do the quadratic equation formula.

tweeetypooh
Feb 27, 2007, 11:56 PM
Can somebody please explain to me how to solve this algebraically to find the x-intercepts?

x squared - 5x = -6

Sorry, I forgot it. XP
Try visiting this site. Just click on the link.. Solving quadratic equations (http://home.alltel.net/okrebs/page6.html)

cool_dude
Feb 28, 2007, 12:22 PM
Darn I got to stop using "he". Sorry about that. By the way your brother is wrong.

peachesapples123
Mar 4, 2007, 01:17 PM
Umm... There's a lot of messages so I won't reply to all of them but thanks for the help, tweetypooh.

Yes, I think I know that now.