Algebra - Expanding
"Expanding" means removing the ( ) ... but you have to do it the right way!
( ) are called "parentheses" or "brackets"
Whatever is inside the ( ) needs to be treated as a "package".
So when you multiply, you have to multiply by everything inside the "package".
Example: Expand 3 × (5+2)
3 × (5+2) = 3 × 5 + 3 × 2
It is now expanded.
You could also go on to calculate that it equals 15 + 6 = 21
In Algebra putting two things next to each other usually means to multiply.
So 3(a+b) means to multiply 3 by (a+b)
Here is an examle of expanding, using variables a, b and c instead of numbers:
And here is another example involving some numbers. Notice that I use a "·" between the 3 and 6 to mean multiply, so 3·6 = 18:
You will often need to multiply negatives (a negative times a positive gives a negative, but multiplying two negatives gives a positive):
In that case -3 · -5 = +15 (a positive answer), but here is another example where the second part is negative:
So the second term ended up negative because 2x · -a = -2ax, (I also thought it neater to write "-2ax" rather than "-2xa").
That was also interesting because I had to handle x being squared (x2)
Lastly, we have an example with three terms inside:
The same rule applies: multiply by everything inside the ().
And here is a hint: if a multiplication is obvious (like a · 2) do it straight away, but if it needs more thought (like a · -b) leave it for the next line.
Multiply by everything inside the ()
Do it in two stages:
- Write down the multiplications
- Then do the multiplications