71. 2x² — 7x + 5 ≤ 0
(x — a)(x — b) ≤ 0
2x² — 7x + 5 = 0
D = b² — 4ac = 49 — 4 * 2 * 5 = 9
x₁ = -b — √D / 2a = 7 — 3 / 4 = 1
x₂ = -b + √D / 2a = 7 + 3 / 4 = 5/2
(x — 1)(x — 4) ≤ 0
x ∈ [1; 5/2]

72. 5x² + 7x + 2 < 0
(x — a)(x — b) < 0
5x² + 7x + 2 = 0
D = b² — 4ac = 49 — 4 * 5 * 2 = 9
x₁ = -b — √D / 2a = -7 — 3 / 10 = -1
x₂ = -b + √D / 2a = -7 + 3 / 10 = -2/5
(x + 1)(x + 2/5) < 0
x ∈ (-1; -2/5)

73. x² + 2x + 15 > 0
(x — a)(x — b) > 0
x² + 2x + 15 = 0
D = b² — 4ac = 4 — 4 * 1 * 15 = -56
x ∈ ∅
Լուծում չունի

74. x² + x + 2 > 0
(x — a)(x — b) > 0
x² + x + 2 = 0
D = b² — 4ac = 1 — 4 * 1 * 2 = -7
x ∈ ∅
Լուծում չունի

75. 2x² + 2x + 5 ≥ 0
(x — a)(x — b) ≥ 0
2x² + 2x + 5 = 0
D = b² — 4ac = 4 — 4 * 2 * 5 = -36
x ∈ ∅
Լուծում չունի