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Q : 1     Use a suitable identity to get each of the following products. 

            (x) (7a-9b)(7a-9b)

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(7a-9b) \times (7a-9b) = (7a-9b)^{2}


We use identity II for this which is 
                                                      (a-b)^{2} =a^{2}-2ab + b^{2}
In this a = 7a and b = 9b  
                                        (7a-9b)^{2} =(7a)^{2}-2(7a)(9b) + (9b)^{2}
                                                                =  49a^{2}-126ab + 81b^{2}

Posted by

Gautam harsolia

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