Tính giá trị của biểu thức A

Given: a - b + c = 0, c = 5d

We can rewrite the first equation as: a + c = b

Substitute c = 5d into the equation a + c = b, we get: a + 5d = b

Now, let's substitute the values of a, b, c into the expression A:

A = (1 - a/b)(1 - b/c)(1 + c/a)(a - b/d - 4)

Substitute a = b - c and c = 5d into the expression A:

A = (1 - (b - 5d)/b)(1 - b/(5d))(1 + 5d/(b - 5d))(b - (b - 5d)/d - 4)

Simplify the expression:

A = (1 - 1 + 5d/b)(1 - b/(5d))(1 + 5d/(b - 5d))(b - b/d + 5 - 4)

A = (5d/b)(1 - b/(5d))(1 + 5d/(b - 5d))(b - b/d + 1)

A = (5d/b)(1 - 1)(1 + 1)(b - b/d + 1)

A = 0

Therefore, the value of the expression A is 0.