<prompt> Chaguo za kukokotoa fx zinatosheleza3fx - 2 f kushoto frac1x kulia xkwa yote x neq 0. Tafuta f4.  <response>: Kuweka x 4, tunapata3f4 - 2 f kushoto frac14 kulia 4.Kuweka x frac14, tunapata3 f left frac14 kulia - 2f4 frac14.Tunaweza kuona milinganyo hii kama mfumo katika f4 na f left frac14 kulia. Kutatua mfumo huu, tunapata f4 frac52. 