Quadratic inequality and its solution
Answers are for parents and teachers.
1
Solve x² − 3x − 10 < 0.
−2 < x < 5
2
Solve x² + 2x − 15 ≥ 0.
x ≤ −5 or x ≥ 3
3
Solve −x² + 5x − 6 > 0.
2 < x < 3
4
The height of a ball thrown upward after t seconds is h = 20t − 5t² (m). During which time interval is the ball higher than 15 m?
20t − 5t² > 15, t² − 4t + 3 < 0, so 1 < t < 3 (from 1 s to 3 s)
5
Does x² + 1 < 0 have a solution? Explain.
No: x² ≥ 0, so x² + 1 ≥ 1 > 0.