If the operation ∆ is defined by a ∆ b = (b - a)^2/a^2 for all numbers a and b, and a ≠ 0, then what is the result when we evaluate this expression: (-5) ∆ (5 ∆ −5) ?  Choose the correct choice from the following answers.
A) 49/9
B) 49/16
C) 81/16
D) 81/25
E) 100/81
(-5) ∆ (5 ∆ −5) =   (-5) ∆ (10^2/5^2) =   (-5) ∆ (4) =   (-9^2) / (-5)^2 = 81/25   The answer is 81/25.
<result>D</result>
If the operation ∆ is defined by a ∆ b = (b - a)^2/a^2 for all numbers a and b, and a ≠ 0, then what is the result when we evaluate this expression: (-5) ∆ (5 ∆ −5) ?