Question

Which number from the set {1, 2, 3,4} makes the inequality 5x² > 12x + 9 true for x?

Is it 1 or 2 or 3 or 4?

Answer 1

4

Explanation:

substitute the values from the set into the inequality and check validity.

x = 1

5(1)² > 12(1) + 9

5(1) > 12 + 9

5 > 21 ← False

x = 2

5(2)² > 12(2) + 9

5(4) > 24 + 9

20 > 33 ← False

x = 3

5(3)² > 12(3) + 9

5(9) > 36 + 9

45 > 45 ← False

x = 4

5(4)² > 12(4) + 9

5(16) > 48 + 9

80 > 57 ← True

thus the value 4 from the set makes the inequality true