Turn on thread page Beta
    • Thread Starter
    Offline

    14
    ReputationRep:
    Show that
    x²-(x-1)²=2x-1

    Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.
    Offline

    15
    ReputationRep:
    multiply out the brackets you will end up with x² minus x² so they cancel out and leave just the 2x - 1
    • PS Helper
    Offline

    2
    ReputationRep:
    PS Helper
    (Original post by Implo)
    Show that
    x²-(x-1)²=2x-1

    Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.

    Begin by expanding the brackets:
    x² - [(x-1)(x-1)] = LHS
    x² - [ x² - x - x + 1 ] = LHS
    x² - x² + x + x + 1 = LHS

    Therefore

    2x + 1 = x²-(x-1)² = RHS

    This is basic multiplying out. Revise factorising quadratics
    Offline

    10
    ReputationRep:
    (x-1)² means (x-1)(x-1).
    Can you multiply out two brackets?
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by Coke Or Pepsi)
    Begin by expanding the brackets:
    x² - [(x-1)(x-1)] = LHS
    x² - [ x² - x - x + 1 ] = LHS
    x² - x² + x + x + 1 = LHS

    Therefore

    2x + 1 = x²-(x-1)² = RHS

    This is basic multiplying out. Revise factorising quadratics
    How did you get from

    x² - [ x² - x - x + 1 ] = LHS

    to

    x² - x² + x + x + 1 = LHS ?
    If multiplied out how come it isn't minus 1?
    Offline

    0
    ReputationRep:
    it is minus 1, he just made a little mistake
    x²-(x-1)²=2x-1
    x²-(x-1)(x-1)=2x-1
    x²-(x²-2x+1)=2x-1
    x²-x²+2x-1=2x-1
    2x-1=2x-1
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Implo)
    Show that
    x²-(x-1)²=2x-1

    Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.
    A "cuter" way to do it is to recognise the difference of two squares.

    a^2 - b^2 = (a + b) (a - b)

    x^2 - (x - 1)^2 = (x + (x - 1)) (x - (x - 1)) = 2x - 1
    Offline

    9
    ReputationRep:
    x²-(x-1)²=2x-1 --->> 80085
    • PS Helper
    Offline

    2
    ReputationRep:
    PS Helper
    (Original post by genericusrnme)
    it is minus 1, he just made a little mistake
    x²-(x-1)²=2x-1
    x²-(x-1)(x-1)=2x-1
    x²-(x²-2x+1)=2x-1
    x²-x²+2x-1=2x-1
    2x-1=2x-1
    She**

    Yes sorry! Typo!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 14, 2011

University open days

  • University of Lincoln
    Mini Open Day at the Brayford Campus Undergraduate
    Wed, 19 Dec '18
  • University of East Anglia
    UEA Mini Open Day Undergraduate
    Fri, 4 Jan '19
  • Bournemouth University
    Undergraduate Mini Open Day Undergraduate
    Wed, 9 Jan '19
Poll
Did you get less than your required grades and still get into university?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Equations

Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.