The set of all real numbers x for which $x^2-| x+2|+x>0$, is |
$(-∞,-2) ∪ (2,∞)$ $(-∞,-\sqrt{2}) ∪ (\sqrt{2},∞)$ $(-∞,-1) ∪ (1,∞)$ $(\sqrt{2},∞)$ |
$(-∞,-\sqrt{2}) ∪ (\sqrt{2},∞)$ |
In this case, we have $|x+2|=x+2$ $∴x^2-|x+2|+x>0$ $⇒x^2 -(x+2)+x>0$ $⇒x^2-2>0$ $⇒ x<-\sqrt{2}$ or $x>\sqrt{2} ⇒ x∈ (-∞,-\sqrt{2}) ∪(\sqrt{2},∞)$ But, $x+2≥0$ i.e. $x ≥-2$ $∴x∈[-2,-\sqrt{2})∪(\sqrt{2},∞)$ CASE II When $x + 2 < 0$ $|x+2| =- (x+2)$ $∴x^2 -|x+2|+x>0$ $⇒x^2+x+2+x>0⇒ x^2+2x+2>0$ This is true for all real values of x as the discriminant of $x^2 + 2x + 2$ is less than zero. So, $x+2<0$ i.e. $x∈ (-∞,-2)$ is the solution set. Hence, the solution set is $[-2,-\sqrt{2})∪(\sqrt{2},∞)∪(-∞,-2)$ or, $(-∞,-\sqrt{2}) ∪ (\sqrt{2},∞)$ |