(x/2+1)^2<=4
Let's solve in ℝ: (x2 + 1)2 ≤ 4
An even power only depends on the absolute value: (x2 + 1)2 ≤ 4 is equivalent to |x2 + 1| ≤ 2
|A| ≤ B is equivalent to -B ≤ A ≤ B
-2 ≤ x2 + 1 ≤ 2
We add -1 to all three parts of the inequality
-3 ≤ x2 ≤ 1
We divide all three parts by 12, which is positive
-6 ≤ x ≤ 2
▶Solution obtained: x ∈ [-6, 2]