A=(3x+4)(x+3)-(x+3)²

Sagot :

A=(3x+4)(x+3)-(x+3)²
=3x²+9x+4x+12-(x²+6x+9)
=3x²+13x+12-x²-6x-9
=2x²+7x+3
A=(3x+4)(x+3)-(x+3)²
  =(x+3)(3x+4-x-3)
  =(x+3)(2x+1)