[tex]2x^2-x-1\geq 0\\2x^2+x-2x-x\geq0\\x(2x+1)-(2x+1)\geq0\\(2x+1)(x-1)\geq0[/tex]
[tex]\left \{ {{2x+1\geq0} \atop {x-1\geq0} \right. \\\left \{ {{2x+1\leq0} \atop {x-1\leq0}} \right. \\\\\left \{ {{x\geq}-\frac{1}{2} \atop {x \geq1} \right.\\\left \{ {{x\leq}-\frac{1}{2} \atop {x \leq1} \right.[/tex]
x∈ {1, +∞)
x ∈ (-∞, -½}
x∈ (-∞, -½} ∪ {1, +∞)
