2+|1-x/2 |>= 5
1) Let's solve in ℝ: 2 + |1 -x2| ≥ 5
ⓘ We subtract 2 from both sides
|1 -x2| ≥ 5 -2
ⓘ Start from 5 and move back 2 on the number line: 5 -2 = 3
|1 -x2| ≥ 3
|A| ≥ B means that: A ≥ B or A ≤ -B
2) Let's solve in ℝ: 1 -x2 ≥ 3
ⓘ We subtract 1 from both sides
-x2 ≥ 3 -1
ⓘ Start from 3 and move back 1 on the number line: 3 -1 = 2
-x2 ≥ 2
ⓘ We multiply both sides by 2
-x ≥ 2·2
ⓘ A single minus sign does not cancel out, the product of a negative number by a positive number is negative: -2·2 = -4
-4
ⓘ We add x to both sides
-4 ≥ x
Solution found: x ≤ -4
3) Let's solve in ℝ: 1 -x2 ≤ -3
ⓘ We subtract 1 from both sides
-x2 ≤ -3 -1
ⓘ Start from -3 and move back 1 more on the number line, away from zero: -3 -1 = -4
-x2 ≤ -4
ⓘ We multiply both sides by 2
-x ≤ 2·(-4)
ⓘ Two minus signs cancel out, the product of two negative numbers is positive: -2·(-4) = 8
8
ⓘ We add x to both sides
8 ≤ x
Solution found: x ≥ 8
▶Solution:   x ∈ (-∞, -4] ∪ [8, +∞)