1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Formula for a square

  1. Jul 25, 2003 #1

    MathematicalPhysicist

    User Avatar
    Gold Member

    [(x3-x2)+(x2-x1)]*[(x3+x2)+(x2-x1)]
    the book expands it to:
    (x3-x2)^2+2(x3-x2)*(x2-x1)+(x2-x1)^2

    i didnt get it so can someone please help me in this, i think there is a mistake in the book.
     
    Last edited by a moderator: Feb 5, 2013
  2. jcsd
  3. Jul 25, 2003 #2
    Re: question

    [(x3-x2)+(x2-x1)]*[(x3+x2)+(x2-x1)] does not equal to(x3-x2)^2+2(x3-x2)*(x2-x1)+(x2-x1)^2

    However,
    [(x3-x2)+(x2-x1)]*[(x3-x2)+(x2-x1)] = (x3-x2)^2+2(x3-x2)*(x2-x1)+(x2-x1)^2
     
  4. Jul 25, 2003 #3

    MathematicalPhysicist

    User Avatar
    Gold Member

    Re: Re: question

    have you noticed the experssions on the right are the same?
     
    Last edited: Jul 25, 2003
  5. Jul 25, 2003 #4
    Please read the expressions on the left hand sides carefully. I changed a "+" sign to a "-" sign in the third small bracket
     
  6. Jul 25, 2003 #5

    MathematicalPhysicist

    User Avatar
    Gold Member

    yes you are right. i guess it was a type mistake )-:
     
  7. Jul 25, 2003 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    With the negative, it is simply the formula for a square:

    (a+b)*(a+b)= a2+ 2ab+ b2

    with a= x3-x2 and b= x2- x1
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook