# Solving exponential system of equations

I am trying to solve equation:

Solve[{y1 == -a*Exp[-b*x1], y2 == -a*Exp[-b*x2]}, {a, b}]

using Solve method but I receive error: Solve::ivar: E^kb t is not a valid variable.I am not reallty sure why I receive this kind of error and how can I make mathematica solve this equation.

• Maybe you had a prior definition such as a=t*Exp[kb]? – Daniel Lichtblau Mar 2 '18 at 19:10

Solve[{y1 == -a*Exp[-b*x1], y2 == -a*Exp[-b*x2]}, {a, b}, Reals]