Question

Resolvam por favor 2x² -x -1=0

Answer 1

$2x^2-x-1=0$

$\Delta=(-1)^2-4\cdot2\cdot(-1)=1+8=9$

$x=\dfrac{-(-1)\pm\sqrt{9}}{2\cdot2}=\dfrac{1\pm3}{4}$

$x'=\dfrac{1+3}{4}=\dfrac{4}{4}=1$

$x"=\dfrac{1-3}{4}=-\dfrac{2}{4}=-\dfrac{1}{2}$.

$S=\{-\frac{1}{2},2\}$