It's not possible to determine the _exact_ equation of the exponential function with certainty from just the given graph and one clear point. However, a likely candidate considering its properties is something of the form y = -6(1/2)^x - 10 or a similar form with a different value for b (where 0 < b < 1) but a clear horizontal asymptote at -10. We would need at least one more point to pinpoint the exact equation.