Question

Determine as raízes das equações abaixo

a)2x² + 8x + 8 = 0

b)81 + 18x + x² = 0​

Answer 1

RESPOSTA:

A)2x² + 8x + 8 = -2

b)81 + 18x + x² = 0-9

EQUAÇÃO:

a)2x² + 8x + 8 = -2

$2x^2+8x+8=0\quad :\quad x=-2\\\\2x^2+8x+8=0$

$x_{1,\:2}=\frac{-b\pm \sqrt{b^2-4ac}}{2a}\\\\8^2-4\cdot \:2\cdot \:8=0\\\\x_{1,\:2}=\frac{-8\pm \sqrt{0}}{2\cdot \:2}\\\\x=\frac{-8}{2\cdot \:2}$

$\frac{-8}{2\cdot \:2}=-2\\\\x=-2$

b)81 + 18x + x² = -9

$81+18x+x^2=0\quad :\quad x=-9\\\\81+18x+x^2=0\\\\x_{1,\:2}=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

$18^2-4\cdot \:1\cdot \:81=0\\\\x_{1,\:2}=\frac{-18\pm \sqrt{0}}{2\cdot \:1}\\\\x=\frac{-18}{2\cdot \:1}\\\\\frac{-18}{2\cdot \:1}=-9\\\\x=-9$