Question

The value of x, when (625)^-(5-x) =5^-20
(A) x = 0
(C) x = 3
(B) =2
(D) = 5​

Answer 1

Answer:

My answer is B as well. Got there by simplifying to the same bases, as above!

625^(-x) + 25^(-2x) + 5^(-4x) = 15

becomes

(5^4)^-x) + (5^2)^(-2x) + 5^(-4x) = 5 * 3

becomes

5^-4x * 3 = 5 * 3

Now we can solve for x:

-4x = 1

x = -1/4