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Consider the polynomials:
A(x) = (3-x)2² - (x-3) (7x+4)-18+2x²
B(x) = (3x + 2)² - (x - 1)²
1) Develop and reduce A (x).
2) Factorize A (x) and B (x).
3) Solve the equation A (x)= B(x)
4) Prove that B (X) -3 = 2x(4x+7) , then solve the equation B(x) =3


Sagot :

Answer:

1)  -5x² + 13x + 6

2) B(x)  =(4x + 1 )(2x + 3)

  A(x) = (5x +2)(3-x)

Step-by-step explanation:

1) Expand the equation by using distributive property. Then simplify  by combining the like terms.

A(x) = (3 -x)2² - (x -3)(7x+ 4) - 18 + 2x²

         = (3 - x)4 - [x*7x + x*4 - 3*7x - 3*4] - 18 + 2x²

         = 3*4 - x*4 - [7x² + 4x - 21x - 12] - 18 + 2x²

         = 12 - 4x - 7x² - 4x + 21x + 12 - 18 + 2x²

        = 2x² - 7x² -4x - 4x + 21x + 12 + 12 - 18

       = -5x² + 13x + 6

B(x) = (3x + 2)² - (x - 1)²

Identities:

(a + b)² = a² + 2ab + b² ; Here a =3x & b = 2

(m -n)² = m² - 2mn + n² ; Here m = x & n = 1

2) B(x) = (3x)² + 2*3x*2 + 2² - [x² - 2*x*1 + 1]

      = 9x² + 12x + 4 - [x² - 2x + 1]

      = 9x² + 12x + 4 - x²+ 2x - 1

     = 9x² - x² + 12x + 2x  + 4 - 1

     = 8x² + 14x +3

Product = 8*3 = 24

Sum = 14

Factors = 2 , 12    {2*12 = 24 & 2 +12= 14}

    = 8x² + 2x + 12x + 3    {Rewrite the middle term}

    = 2x(4x + 1) + 3(4x + 1)      

   = (4x + 1 )(2x + 3)

  A(x) = - 5x² + 13x + 6

       = -5x² + 15x -2x + 6

       = 5x(-x +3) +2 (-x + 3)

       = (5x +2)(3-x)

4) B(x) - 3 = 8x² + 14x + 3 - 3

                = 8x² + 14x

                = 2x *4x + 2x *7

                =2x(4x + 7)

Hence proved.

                           B(x) = 3

            8x²  + 14x + 3 = 3

        8x² + 14x + 3 - 3 = 0

           8x² + 14x         = 0

              2x(4x + 7)     = 0

2x = 0   or    4x + 7 = 0

 x = 0   or          4x = -7

                            [tex]\sf x = \dfrac{-7}{4}[/tex]

  x = 0 or    [tex]\sf \dfrac{-7}{4}[/tex]