Silverton County is home to a declining population of sage grouse, an endangered species of land bird similar to turkeys. Every decade, the Silverton Wildlife Center publishes its estimate of the county's sage grouse population. The most recent estimate, published this year, concluded that there are about 115,000 sage grouse in the county, and the population is expected to decrease by a factor of 1/4 each decade.
Write an exponential equation in the form y=a(b)x that can model the estimated population of sage grouse in Silverton County, y, in x decades.
Use whole numbers, decimals, or simplified fractions for the values of a and b.