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The set of all real values of xx for which (x2−∣x+9∣+x)>0(x^2 - |x + 9| + x) > 0, is

Solution

✅ Correct Option: 4

Since there is an absolute value ∣x+9∣|x + 9|, split into two cases based on the sign of (x+9)(x + 9).


When x≥−9x \geq -9, ∣x+9∣=x+9|x+9| = x+9:

x2−(x+9)+x>0x^2 - (x + 9) + x > 0

x2−x−9+x>0x^2 - x - 9 + x > 0

x2−9>0x^2 - 9 > 0

(x−3)(x+3)>0(x-3)(x+3) > 0

This is positive when x<−3x < -3 or x>3x > 3.

Applying the restriction x≥−9x \geq -9, the solution from this case is [−9,−3)∪(3,∞)[-9, -3) \cup (3, \infty).


When x<−9x < -9, ∣x+9∣=−(x+9)|x+9| = -(x+9):

x2+(x+9)+x>0x^2 + (x+9) + x > 0

x2+2x+9>0x^2 + 2x + 9 > 0

(x+1)2+8>0(x+1)^2 + 8 > 0

Since (x+1)2≥0(x+1)^2 \geq 0, this expression is always ≥8>0\geq 8 > 0, so the inequality holds for all x<−9x < -9.

The solution from this case is (−∞,−9)(-\infty, -9).


Combining both cases:

(−∞,−9)∪[−9,−3)∪(3,∞)(-\infty, -9) \cup [-9, -3) \cup (3, \infty)

=(−∞,−3)∪(3,∞)= (-\infty, -3) \cup (3, \infty)

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