If y = x2 - x - 12, find the range of values of x for which y ≥
0
A.
x < -3 0r x > 4
B.
x ≤ -3 or x ≥ 4
C.
-3 < x ≥ 4
D.
-3 ≤ x ≤ 4
Correct Answer: x ≤ -3 or x ≥ 4
Explanation
y = x2 - x - 12
= (x - 4)(x + 3)
∴ x = 4 or x = -3
Checking the cases for y ≥
0
We check values on the range x - 4 ≥
0; x + 3 ≤
0; x - 4 ≤
0 and x + 3 ≥
0 for the range which satisfies the inequality x2
- x - 12 ≥ 0.
We find that the inequality is satisfied on the range x ≤ -3 and x ≥
4.
y = x2 - x - 12
= (x - 4)(x + 3)
∴ x = 4 or x = -3
Checking the cases for y ≥
0
We check values on the range x - 4 ≥
0; x + 3 ≤
0; x - 4 ≤
0 and x + 3 ≥
0 for the range which satisfies the inequality x2
- x - 12 ≥ 0.
We find that the inequality is satisfied on the range x ≤ -3 and x ≥
4.