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SAI International School
                                                    CLASS – VIII,
           SUB: MATH

           LESSON NOTES-5
           Ch-14: FACTORISATION

           SUBTOPIC:
               Factorisation using identity (      )


                     1. Factorisation using identity (      )


                         (      ) is the third identity.


                         Let’s find that whether this identity is true or not,
                         First take the right hand side of the identity and do the multiplication.
                         RHS:-
                                                            ᶐ
                                                      = Ǥ     Ǥ  ᶐ  Ǥ     Ǥ

                                                      =        ᶐ

                                                      =
                                                      = LHS (left hand side)
                        As you see to find the factorisation of       , I don’t have any method


                        So this is a special type of factorisation where we have to look for two square

                         numbers and they should in the form of       Ǥ
                        Then we can use this identity without any calculation.
                     Example:-
                     1. Find the value of 95 x 105.
                         Answer:
                         Using the identity a – b = (a – b)(a + b),
                                             2
                                                  2
                                                                                     2
                         95 x 105 may be written as (100 – 5)(100 + 5) = 100 – 5 = 10000 – 25 = 9975
                                                                                2
                     2. Simplify: (3 – 2x)(3 + 2x).
                         Answer:
                         9 – 4x .
                                2
                         Here a=3 and b= 2x

                         Apply identity find    ᶐ    Ǥ




                                   and       ्     ्
                  Useful Link Video- https://www.youtube.com/watch?v=24rx11nCFS8
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