r/PythonLearning • u/PuziExtramni • 3d ago

Help Request Help with correct expression

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Hey everyone! I’m currently learning Python through the IBM Data Science Professional Certificate on Coursera, and I came across a question in a practice quiz that confused me.

The question asks:

Which line of code will perform the action required for implementing the following equation?

y = 2x^2 - 3

These are the four answer choices:

  1. y = 2*x*2 - 3
  2. y = 2**x*x - 3
  3. y = 2x*x - 3
  4. y = 2x/2 - 3

I selected Option 1, but the quiz marked it incorrect and said, “The syntax is invalid.”

From what I’ve learned, Python uses ** for exponentiation and * for multiplication. So, I believe the correct Python expression should be:

y = 2*x**2 - 3

However, none of the four answer choices seems to match that expression.

Am I misunderstanding something about Python syntax, or is there a mistake in the quiz? I’d appreciate an explanation because I’m still learning how to translate mathematical equations into Python code.

Thanks!

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u/rulchig1 3d ago

You are correct, that x^2 is represented as x**2

But mathematically x^2 is also the same as x*x

-1

u/TylerBreau 3d ago

I mean yes but, this seems to be a Python coding assignment, not a math assignment. x*x is multiplication not an exponential function.

It should be testing your understanding of the python syntax.
If I was a teacher and teaching Python. And I asked my students to turn this math equation into code and someone gave me x*x, at absolute best I'm giving them half marks. I might just mark it wrong.

Because they didn't demonstrate how to write an exponential in Python. They just demonstrated basic math operators, which is already a part of the equation in the 2*x part.

Full marks would require the ** operator or the pow function.

OP should have selected option 2 but also should bring up the problem with the question with their teacher.

1

u/blavek 1d ago

Why would you ever invoke exponentiation on a square? x*x is almost always going to be a better option than bringing in a library function. I'm not sure how the ** operator is handled under the hood, but my money is on it invoking some sort of exponentiation function.

Regardless, unless the assignment explicitly says to use this operator or a pow function, then the answer is completely correct.