Question

determine as raízes reais das equações incompletas .
j) 2x(x+1)=x(x+5)+3(12-x)

Answer 1

$2x \cdot(x + 1) = x\cdot (x + 5) + 3 \cdot (12 - x)\\ \\2x^2 + 2x = x^2 + 5x + 36 - 3x\\ \\2x^2 + 2x - x^2 - 5x - 36 + 3x=0\\ \\2x^2 - x^2 + 2x - 5x + 3x - 36=0\\ \\x^2 - 36=0\\ \\x^2=0+36\\ \\x^2=36\\ \\x=\pm\sqrt{36}\\ \\x=\pm6\\ \\S=\{ \pm6\}$