More advanced sign rules for addition and subtraction...Often in an math problem with addition and subtraction of positive and negative numbers the signs and operators can become confusing. I'm going to teach you a fast way to take (what I call) 'double signs' and simplify to a single sign so the problem will be more manageable.
Let's look at this example:
-4 + (-3) here we have a negative 4 being added to a negative 3. There are several ways to think about this type of problem, but the easiest way for some students is to use multiplication rules to simplify the double signs. We know the multiplication rules are:
(+)(+) = + When there are two signs next to each other in addition or subtraction
(-)(-) = + we can remember these rules and use them to pick just ONE sign to use
(-)(+) = - when we rewrite the problem.
So -4 + (-3) has a positive (or plus) sign next to a negative sign. A negative and a positive sign simplify to a negative sign.
The problem can be rewritten as -4 - 3. Using the rules we learned in an early blog post, these two numbers have the same signs and we will add the numbers and keep the sign. So the answer is -7.
This website (click here) has a nice explanation of these types of problems and shows several different examples broken down for you.
This website (click here) has endless practice problems for you to try. You can enter your answer into their website and they will check your work right away. Check it out - it's very useful!
Here is a worksheet that you can try to make sure that you are beginning to grasp the concept. The answers are included after the worksheet (click here)
And as always, if you need any additional help, stop by the Learning Lab department and make a tutoring appointment!