The set of all real numbers x for which \( \Large x^{2}-|x+2|+x>0 \) is:

A) \( \Large \left(-\infty, -2\right) \ \left(2, \infty\right) \)

B) \( \Large \left(-\infty, -\sqrt{2}\right) \ \left(\sqrt{2}, \infty\right) \)

C) \( \Large \left(-\infty, -1\right) \ \left(1, \infty\right) \)

D) \( \Large \left(\sqrt{2}, \infty\right) \)

Correct answer:
B) \( \Large \left(-\infty, -\sqrt{2}\right) \ \left(\sqrt{2}, \infty\right) \)

Description for Correct answer:

Given \( \Large x^{2}-|x+2|+x>0 \)

we know that\( \Large |x+2|=\pm \left(x+2\right) \)

If \( \Large |x+2|=-x+2x\ge -2 \)

Equation (i) becomes \( \Large \left(when\ x \ge - 2 \right) \)

\( \Large x^{2}-x-2+x>0 \)

\( \Large x^{2}-2 > 0 \)

=> \( \Large x < -\sqrt{2}\ or\ x > \sqrt{2} \)

\( \Large x \epsilon \left[ -2, -\sqrt{2} \right] \cup \left(\sqrt{2}, \infty\right) \)

If therefore, equation (i) becomes

\( \Large x^{2}+x+2+x>0\ when\ x \le -2 \)

\( \Large x^{2}+2x+2 > 0\ when\ x \le -2 \)

\( \Large \left(x+1\right)^{2}+1 > 0\ when x \le -2 \)

which is true for all x.

\( \Large x < -2\ or\ x \left(-\infty,\ -2\right) \)

from equations (ii) and (iii)

\( \Large x \epsilon \left(-\infty,\ -\sqrt{2} \right) \cup \left(\sqrt{2},\ \infty\right) \)



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