These are basically the same as multiplying normal fractions, only with variables in them. I would advise looking at multiplying fractions first, if you don't know how.
Calculate 1 / χ + 4 x 3χ / χ + 2
Ok, so first we multiply our numerators together:
1 x 3χ = 3χ
And now our denominators:
χ + 4 x χ + 2 = (χ + 4)(χ + 2)
We don't need to expand the brackets here (as it's in a fraction). This gives us a final value of:
3χ
(χ + 4)(χ + 2)
This cannot be simplified any more - some students mistakenly cancel χ, but you can't do this because you can only cancel if the same bracket is on both the top and bottom, like this:
3χ (χ + 4)
(χ + 4)(χ + 2)
In which case you cound cancel (χ + 4) to make 3χ / χ + 2. You can test yourself on this here:
Commentaires