I appreciate this is very simple, but I'm experiencing a very basic problem with fractions containing variables and I'd just like to check I'm along the right lines. In the following instance:
$ \frac{2(x+7)(3x+1)}{2} = \frac{2}{2} \cdot \frac{2(x+7)(3x+1)}{1} = (x+7)(3x+1)$
Does the $\frac{2(x+7)(3x+1)}{1}$ have a denominator of 1 because we have factored out the 2 in the prior step?
You made a mistake, you have:
$$\frac{2(x+7)(3x+1)}{2}=\frac 22\cdot\frac {(x+7)(3x+1)}{1}=1\cdot(x+7)(3x+1)=(x+7)(3x+1)$$
instead of what you wrote.