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2015-09-05T01:22:15+08:00

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1) (5x-4) (5x+4) = 25x² + 20x-20x - 16
                             = 25x² -16

2)  (a + b -c) (a + b + c)
     a² + ab + ac + ab + b² + bc -ac - bc -c²
     a² + 2ab +b² - c²

3) (2x+3y-4z)²  
    Expand
    (2x + 3y - 4z) (2x+3y-4z)
     Multiply each term  in first trinomial by each term in second trinomial.  This is similar to number 2.

4.  (3-5y)² = Expand  (3-5y) (3-5y)
                                     = 9 -15y - 15y + 25y²
                                     = 9-30y + 25y²
                                        25y² -30y + 9

5)   (x²-3)³ = (x² - 3) (x²-3) (x²-3) 
                  = x^6  - 6x^4-3x^4 + 9x² + 18 x² - 27
                    x^6 -9x ^4 + 27x² - 27

You can do the rest :-)


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