Sometimes substitution will include negative numbers. When you substitute in a negative value you need to be careful with how this affects the expression:
Adding a negative number is the same as taking away a positive number:
eg \(10+(-3)\) is the same as \(10-3\)
Subtracting a negative number is the same as adding a positive number:
eg \(10-(-3)\) is the same as \(10+3\)
Example
If \(x~=~-3\) and \(y~=~6\)
Find \(2x~-~y\)
How to solve the expression:
\(2x~-~y\)
Substitute \(x\) with the value \(-3\) and \(y\) with \(6\)
