Beginning Algebra ch1.5

# Beginning Algebra ch1.5 - what’s going on Now though...

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Beginning Algebra MTH 095 FALL 2011 Moraine Valley Community College Chapter 1.5: Adding (and Subtracting) Real Numbers What I’m about to show you isn’t difficult but it might require a little bit of practice. It’s how to add and subtract numbers with basically two different signs. Here we go! How this is going to work: I’m not going to tell you the rules. I’m just going to write down some true statements and I’m going to see if you can pick out the rules for yourself. Sounds good? Excellent! (Because, you know, I can’t hear you if you say it _doesn’t_ sound good. Case I 3 + 7 = 10 -3 + -7 = -10 -4 + -5 = -9 4 + 5 = 9 -6 + -2 = -8 6 + 2 = 8 Did you notice a pattern? That’s right! All the examples have the same signs on them! A positive plus a positive equals a positive (you already knew that!), and a negative plus a negative equals a negative. It’s simple once you realize

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Unformatted text preview: what’s going on! Now, though, let’s talk about what happens when things get a little mixed up: Case II-5 + 8 = 3 5 + -8 = -3 12 + -6 = 6-12 + 6 = -6 Now we need a little extra to help us understand things. I call this the Arm-Wrestling Rule but you can call it whatever you like. Here’s how it goes (we’ll break down one problem) 5 + -8 You can think of this as an absolute value problem (it works just as well) but ask yourself: which number looks stronger to you: the 5 or the -8? The -8 looks stronger. Strong – Weak Following this we do Strong – Weak, ignoring the signs. In This case that would leave this problem as 8 – 5, or 3.-3 We put the sign of the stronger number on there. In this case it was negative, so our answer is -3. FINAL ANSWER Makes sense? Drop me a line if it’s confusing....
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Beginning Algebra ch1.5 - what’s going on Now though...

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