Find all values of c such that c/(c - 5) = 4/(c - 1). If you find more than one solution, then list the solutions you find separated by commas.
c / ( c - 5) = 4 / (c - 1) cross-multiply
c ( c - 1) = 4(c - 5)
c^2 - c = 4c - 20
c^2 - c - 4c + 20 = 0
c^2 - 5c + 20 = 0 complete the square on c
c^2 - 5c + 25/4 = - 20 + 25/4
(c - 5/2)^2 = -55/4 take both roots
c - 5/2 = ± i sqrt ( 55) / 2
c = 5/2 ± i sqrt (55) /2
