1 Task

Write a file named quadratic.py with a function named big_root which, if given (a, b, c), returns the more positive root of the quadratic equation

a x2 + b x + c = 0

Use the quadratic formula to solve this problem.

Also write a second function, small_root, which gives the other root of the equation.

You may assume we only give coefficients for which the answer is a real number.

Neither function should print anything nor ask for any input. You should not have any code outside of these two functions.

2 Example Invocations

When you run quadratic.py, nothing should happen. It defines a function, it does not run it.

If in another file (which you do not submit) you write the following:

import quadratic

print(quadratic.big_root(1, -1, -1))
print(quadratic.small_root(1, -1, -1))

you should get the following output:

1.618033988749895
-0.6180339887498949

(don’t worry if your answer differs in the last few digits)

3 Thought Question

We won’t grade this, but what does your code do when you try to solve an equation with no real solutions?

print(quadratic.big_root(1, 1, 1))

If you want, feel free to also add the cubic formula or even (if you feel really ambitious) the quartic formula, but there isn’t a quintic formula.

4 Troubleshooting

Recall that .

Don’t remember the operators you need? See §3.3.1. Also, remember that in Python ^ is not the exponentiation operator (we won’t cover what ^ is; if you are curious, see §19.2.5).

Did you get the order of operations right? You could look them up, but adding parentheses never hurts.

There are two roots (because of the ± in the quadratic formula), but one of them is always the biggest… no need for an if

Have you tried other coefficients besides (1, -1, -1)?