Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 27

Thread: I need help-code and math

  1. #11
    Senior Member
    Join Date
    Feb 2015
    Location
    USA
    Posts
    126

    Default Re: I need help-code and math

    It’s been thirty years since I have had to square root anything. I had to look it up. When a number is multiplied by itself is the answer.



    I get that part, it's just like coding.

    Quote Originally Posted by grapes View Post
    Take the square root of both sides.
    I would do this to get rid of the squared on the left to simplify the equation and that would make the 9 on the right 3.

    Quote Originally Posted by grapes View Post
    The square root of the left hand side is easy, the square root is the inverse of the squaring, so all we're left with is (3x-5), with two possibilities, that it could be the positive or the negative square root.
    Negative and positive possibilities could happen in other equations, and that is why both exist, right?
    Last edited by Eleftherios Karagiannis; 06-05-2015 at 09:36 PM.
    Sometimes, the logical answer defies logic....Stupid accident.

    If my thoughts are math, how can I be wrong?

  2. #12
    Moderator grapes's Avatar
    Join Date
    Nov 2010
    Location
    NC USA
    Posts
    4,005

    Default Re: I need help-code and math

    The point is, what we do to the equation can affect the solution, and we sometimes have to account for those changes.

    For instance, x=3 is a simple equation that has a simple solution. There is only one value for x that makes it true, and that value is 3. If we were to square both sides, we get which has two solutions, 3 and -3. By squaring both sides, we've introduced the possibility of a solution that wasn't a solution to the original. Similarly, when we take the square root of both sides, we have to remember to keep both solutions.

    That's what we mean by the plus/minus sign in

  3. #13
    Senior Member
    Join Date
    Feb 2015
    Location
    USA
    Posts
    126

    Default Re: I need help-code and math

    Quote Originally Posted by grapes View Post
    The point is, what we do to the equation can affect the solution, and we sometimes have to account for those changes.

    For instance, x=3 is a simple equation that has a simple solution. There is only one value for x that makes it true, and that value is 3. If we were to square both sides, we get which has two solutions, 3 and -3. By squaring both sides, we've introduced the possibility of a solution that wasn't a solution to the original. Similarly, when we take the square root of both sides, we have to remember to keep both solutions.

    That's what we mean by the plus/minus sign in
    That makes sense to me.
    Sometimes, the logical answer defies logic....Stupid accident.

    If my thoughts are math, how can I be wrong?

  4. #14
    Moderator grapes's Avatar
    Join Date
    Nov 2010
    Location
    NC USA
    Posts
    4,005

    Default Re: I need help-code and math

    Quote Originally Posted by Eleftherios Karagiannis View Post


    I get that part, it's just like coding.
    So we take the square roots of both sides, keeping both roots:





    Now the parentheses are not necessary



    And we can add 5 to both sides





    Now we divide both sides by 3



    So we end up with a lone x on the left hand side:


  5. #15
    Senior Member
    Join Date
    Feb 2015
    Location
    USA
    Posts
    126

    Default Re: I need help-code and math

    Quote Originally Posted by grapes View Post

    So we end up with a lone x on the left hand side:

    I can follow all that, but highly doubt I could have gotten to x on my own. My goal is to get x all by itself, that helps me better understand, and maybe now I can.

    So x can be or , right? Or am I getting ahead of my self?
    Last edited by Eleftherios Karagiannis; 06-06-2015 at 09:00 AM.
    Sometimes, the logical answer defies logic....Stupid accident.

    If my thoughts are math, how can I be wrong?

  6. #16
    Moderator grapes's Avatar
    Join Date
    Nov 2010
    Location
    NC USA
    Posts
    4,005

    Default Re: I need help-code and math

    Quote Originally Posted by Eleftherios Karagiannis View Post
    I can follow all that, but highly doubt I could have gotten to x on my own. My goal is to get x all by itself.
    It takes a little practice. But you quickly see what has to be done to both sides of the equation so that the variable you are interested in ("x") gets maneuvered to one side by itself.
    So x can be or , right?
    Yes, exactly. And typically you should try them in the original equation to make sure:



    Now, once you're given a formula like that, the steps to solving it are similar.

    Another type of equation that we can solve is of the quadratic form, where each term is either a constant, has a factor of x, or has a factor of x squared:


  7. #17
    Senior Member
    Join Date
    Feb 2015
    Location
    USA
    Posts
    126

    Default Re: I need help-code and math

    Quote Originally Posted by grapes View Post

    I am going to try and solve this on my own, I like trying, even if I am wrong, I will learn along the way, hopefully.

    I will let you know, either way.
    Last edited by Eleftherios Karagiannis; 06-06-2015 at 09:26 AM.
    Sometimes, the logical answer defies logic....Stupid accident.

    If my thoughts are math, how can I be wrong?

  8. #18
    Moderator grapes's Avatar
    Join Date
    Nov 2010
    Location
    NC USA
    Posts
    4,005

    Default Re: I need help-code and math

    Quote Originally Posted by grapes View Post
    It took decades, maybe millennia, but we learned that, in general, we should get all parts to one side. So we subtract one whole side from both sides:



    which will leave zero on one side:



    We can get rid of the parentheses, but notice we are subtracting each term:



    Rearranging:







    At this point, we could use the famous quadratic formula to solve this. That formula says that if , then the solution to it is



    where, in our problem, a=9, b=-30, and c=16

    But, that general solution was found by a method called completing the square, and I will solve our problem by that method.

    OK so far?
    Last edited by grapes; 06-08-2015 at 02:48 AM.

  9. #19
    Moderator grapes's Avatar
    Join Date
    Nov 2010
    Location
    NC USA
    Posts
    4,005

    Default Re: I need help-code and math

    Quote Originally Posted by grapes View Post
    To "complete the square" we add and divide a value to the equation. This value will allow a portion of the expression to be represented as an algebraic square

    The value that we add and subtract is the second coefficient squared, divided by four times the first coefficient. In other words, , which is equal to 25:



    The reason we do this is that makes the first three terms into a perfect algebraic square:



    So we can replace those first three terms with the square:



    Now we add 9 to both sides



    And we've arrived at the same problem that we solved before:


  10. #20
    Senior Member
    Join Date
    Feb 2015
    Location
    USA
    Posts
    126

    Default Re: I need help-code and math

    Wow, that was far harder than I could of imagined, it did not seem that hard when I first saw it. I could not get that far in trying, I failed, that is okay, it was only thinking. Now that I have seen the answer, I have a long road ahead of me to learn this.

    I hope the coding part is easier than this, otherwise, I have two long and hard roads in front of me. All learning is like that, after all.
    Last edited by Eleftherios Karagiannis; 06-11-2015 at 08:22 PM.
    Sometimes, the logical answer defies logic....Stupid accident.

    If my thoughts are math, how can I be wrong?

Page 2 of 3 FirstFirst 123 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •