On an orbital station, Emek and Tara discovered that a damaged solar array was producing too little power for the essential systems. The control panel represented the difference between the required output and the array's output by 2x^2 - 18x + 40, where x was the array's position setting. To restore the required power, this expression had to equal 0. Tara first factored out 2, giving 2(x^2 - 9x + 20) = 0. Emek then factored the quadratic as 2(x - 4)(x - 5) = 0, so the possible settings were x = 4 and x = 5. However, a warning on the damaged positioning mechanism showed that settings above 4.6 could strain its support joint. That ruled out x = 5 even though it satisfied the equation. They substituted x = 4 into the original expression and confirmed that the result was 0. Tara adjusted the array to setting 4, and moments later the station reported that sufficient power had been restored.