a / (1 - a) + b / (1 - b) + c / (1 - c) = 1
Step 1: Express in a Common Form
Rewriting each term:
Let x = a / (1 - a), y = b / (1 - b), and z = c / (1 - c). Then we have:
x + y + z = 1
From the definitions:
a = x / (1 + x),
b = y / (1 + y),
c = z / (1 + z).
We need to determine the value of:
1/a + 1/b + 1/c.
Step 2: Express in Terms of x, y, z
Using the reciprocal:
1/a = (1 + x) / x,
1/b = (1 + y) / y,
1/c = (1 + z) / z.
Thus:
1/a + 1/b + 1/c = (1 + x) / x + (1 + y) / y + (1 + z) / z.
Splitting each fraction:
1/a + 1/b + 1/c = (1/x + 1) + (1/y + 1) + (1/z + 1).
Rewriting:
1/a + 1/b + 1/c = 1/x + 1/y + 1/z + 3.
Step 3: Find 1/x + 1/y + 1/z
Since x + y + z = 1, applying the identity:
1/x + 1/y + 1/z ≥ 9 / (x + y + z) = 9 / 1 = 9.
Thus:
1/a + 1/b + 1/c = 9 + 3 = 12.
Final Answer:
1/a + 1/b + 1/c = 12.