Assignment: Substitution
In Algebra “Substitution” means putting numbers where the letters are:
If you have: x – 2
And you know: x=6
Then you can substitute 6 for x
6 – 2 = 4
Simple, right? It gets a little more complicated. Take a look at the expression:
6a
We’ll say that a=3. It is very important to remember when there is a number right next to variable, it symbolizes multiplication. One of the most common mistakes make is this:
If a = 3 then 6a = 63.
This is not the case. Please, please, please, do not forget that a number next to a variable, such as 6a is the same as saying ’6 times a’. So,
If you have: 6a
And you know: a=3
Then you can substitute 6 for a
6(3) = 6 ∙ 3 = 18
Another example:
If x=5 then what is 10/x + 4 ?
Remember that ‘/’ represents division.
Put “5″ where “x” is:
10/5 + 4 = 2 + 4 = 6
This same concept applies even when there is more than variable.
If x=3 and y=4, then what is x2 + xy ?
Put “3″ where “x” is, and “4″ where “y” is:
32 + 3×4 = 3×3 + 12 = 21