您可以使用蛮力方法，在n的不同参数值下测试多次运行。

test <- data.frame(used = c(1.545, 0.125, 0.0548), product = c(3.56, -1.589, 0.878))
params <- seq(0, 4, by = .1) # can try even smaller than 0.1 steps if you wanted
wynik <- rep(NA, length(params)) # initialize results object
for(i in 1:length(params)){
  n <- params[i]
  wynik[i] <- length(which(test$used - n * test$product > 0))
}
cbind(params,wynik)
 #params wynik
 #[1,]    0.0       3
 #[2,]    0.1       2
 #[3,]    0.2       2
 #[4,]    0.3       2
 #[5,]    0.4       2
 #[6,]    0.5       1
 #[7,]    0.6       1
 #...     ...       ...