```{r setup, include=FALSE}
## parameters
a <- sample(2:9, 1)
b <- sample(seq(2, 4, 0.1), 1)
c <- sample(seq(0.5, 0.8, 0.01), 1)
## solution
res <- exp(b * c) * (a * c^(a-1) +
       b * c^a)
```

Question
========
What is the derivative of $f(x) = x^{`r a`} e^{`r b` x}$, evaluated at $x = `r c`$?
A formula is $$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}.$$

Answerlist
----------
* `r fmt(res)`
* `r fmt(a)`
* `r fmt(b)`
* `r fmt(c)`
* `r fmt(a+c)`

Solution
========

There is some feedback here with R `r fmt(res)` and formulae $$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$.

Meta-information
================
exname: Single Choice
extype: schoice
exsolution: 10000
exshuffle: TRUE
