The set of all real numbers x for which $x^2-| x+2|+x>0$, is
Answer & explanation
Correct answer: option 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, $(-∞,-\sqrt{2}) ∪ (\sqrt{2},∞)$