Now, consider the wave function ψ (x) = ceκx+de-κx in the region x<0. as x goes to negative infinity, this must become zero. what does this imply about the constants c and d? (be careful of signs.)

d is zero (0)

Explanation:

ψ (x) = ce^κx+de^-κx

Let say x = - 1000

We have something like

ce^κ * - 1000 = approximately zero

Where we assume k to be 1

C becomes zero as it tend to negative infinity

But

If k is 1

de^-1 * 1000 = d * 2 * 10^434

To have a zero function d = 0

So 0 * 2 * 10^434 = 0