Question

Resolva (3-4x)(x+3)=9

Muito obrigada :)

Answer 1

$(3-4x)(x+3)=9\\ 3x+9-4x^2-12x=9\\ 4x^2-9x+9-9=0\\ 4x^2-9x=0\\\\ a=4\\b=(-9)\\c=0\\\\\Delta=b^2-4\cdot a\cdot c\\\Delta=(-9)^2-4\cdot4\cdot0\\\Delta=81\\\\\dfrac{-(-9)\pm\sqrt{81}}{2\cdot4}\\\dfrac{9\pm9}{8}$

$x'=\dfrac{9+9}{8}=\dfrac{18}{8}=\dfrac{18\div2}{8\div2}=\dfrac{9}{4}$

$x''=\dfrac{9-9}{8}=\dfrac{0}{8}=0$