Question

como resolver essa conta (3x+1)(3x-1)-(3x+1)²

Answer 1

$(3x+1)(3x-1)-(3x+1)^2\\\\ =(3x+1)(3x-1)-(3x+1)(3x+1)$


Colocando o fator comum $(3x+1)$ em evidência,

$=(3x+1)\cdot \left[(3x-1)-(3x+1)\right]\\\\ =(3x+1)\cdot \left[\diagup\!\!\!\!\! 3x-1-\diagup\!\!\!\!\! 3x-1\right]\\\\ =(3x+1)\cdot \left[-2\right]\\\\ =-6x-2$