Understanding the Context

The inequality rac⁻ʙ + b/a – 2 ≥ 0 can be rewritten for clarity:
(1 / (r⁻ʙ)) + (b / a) – 2 ≥ 0

Recall that r⁻ʙ = 1 / rʙ, so this simplifies to:
(rʙ)⁻¹ + (b / a) – 2 ≥ 0

This inequality compares two rational expressions and a constant. The goal is to determine under what conditions the sum of the reciprocal of a ratio rʙ and a ratio b over a exceeds or equals 2.

Step-by-Step Solution

Key Insights

Step 1: Simplify the expression

Rewrite using exponent rules:
(1 / (rʙ)) + (b / a) – 2 ≥ 0
We aim to analyze when this expression is non-negative.

Step 2: Consider symmetry and substitution

Let’s define x = rʙ and y = b / a. Then the inequality becomes:
1/x + y – 2 ≥ 0

This form helps identify relationships between x and y, and how their values determine the inequality.

Step 3: Analyze critical points

Rewriting:
1/x ≥ 2 – y

This inequality holds when both sides are defined and the inequality direction is valid (considering the sign of 2 – y). The domain requires x ≠ 0 (since division by zero is undefined) and y > 0 (since b and a values typically assumed positive in real applications to keep expressions meaningful).

Final Thoughts

Step 4: Consider boundary and equality cases

At equality:
1/x + y = 2

Suppose a = b for simplicity—this symmetric case often reveals key insights. Let a = b. Then y = 1, so:
1/x + 1 = 2 → 1/x = 1 → x = 1

So when a = b, equality holds when rʙ = 1 and b = a.

Step 5: Generalize solution

For rac⁻ʙ + b/a – 2 ≥ 0 to hold, several conditions must be met:

1. rʙ > 0, a > 0 (to keep all expressions defined and positive)
   
2. If 1/x < 2, then y ≥ 2 – 1/x (from 1/x + y ≥ 2)
   
3. If 1/x ≥ 2, then y ≥ 0 — but to keep expressions balanced, y ≥ 0 is acceptable.