Christian Lawson-Perfect

Christian Lawson-Perfect on Completing the square 8 years, 5 months ago

Saved a checkpoint:

I've split the last part, which asked you to find solutions after completing the square, into a separate question.

I moved the "Write the following expression in the form ..." text into the statement, because it's repeated for every part.

The advice now begins with a concise description of completing the square, which means the advice for the individual parts can just show how it's done.

The marking uses string restrictions, which just about does the job - you'd have to give a pretty artifical answer to get away with not completing the square - but it would be better if it did pattern-matching.

Christian Lawson-Perfect on Extract common factors of polynomials 8 years, 5 months ago

Gave some feedback: Ready to use

Christian Lawson-Perfect on Extract common factors of polynomials 8 years, 5 months ago

Saved a checkpoint:

It works!

I've rejigged the advice - each part's advice now begins with a description of the common factors, and I've been very careful about the use of brackets so that it's obvious what "pulling outside the brackets" means.

Christian Lawson-Perfect on Extract common factors of polynomials 8 years, 5 months ago

Saved a checkpoint:

I'm working on writing a script to check that the expression really are factorised. At the moment, it expects the common factor to just be a number, which only works for part a!

Christian Lawson-Perfect on Extract common factors of polynomials 8 years, 5 months ago

Gave some feedback: Has some problems

Christian Lawson-Perfect on Extract common factors of polynomials 8 years, 5 months ago

Saved a checkpoint:

Factorising by finding a common (constant) factor and factorising quadratics are very different tasks. I think the scope of this question is only the first kind.

For example, to factorise $2x + 4y + 16xy$, I only need to see that $2$, $4$ and $16$ have a factor of $2$ in common. To factorise $x^2-1$, I need to know a fact about quadratics: the terms $x^2$ and $1$ don't have a proper factor in common.

So, I'm going to split the qudratics part into a separate question, leaving only the expressions with common factors.

Christian Lawson-Perfect on Using a speed graph to find distance 8 years, 5 months ago

Gave some feedback: Ready to use

Christian Lawson-Perfect on Using a speed graph to find distance 8 years, 5 months ago

Saved a checkpoint:

The area under the flat bits is a rectangle, not necessarily a square!

I've tidied up the wording of the advice in some places, and made sure all the inputs have units after them.