Let f(x) = cx -1.28 and suppose that f(6) = 23. Find the value of c.

f(x) = cx -1.28   so....if x = 6, f(x) = 23 and we have

23 = c(6) - 1.28     add 1.28 to each side

24.28 = c(6)      divide both sides by 6

c = about 4.046