Addition and Multiplication Principles

ErinT

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Dec 10, 2009
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Solve using the addition and multiplication principles:
4+5x < 29
 
Solve using the addition and multiplication principles:
4+5x < 29

When we say “solve for x,” it means we want to get x by itself on one side of the equation (or, in this case, the inequality). We see that we have two terms on the left hand side – the 4, and the 5x. To start, get rid of the term that does not contain x (the “4” in other words). Since it is a positive 4, we will get rid of it by subtracting 4 from each side of the equation/inequality:

4+5x < 29
4 – 4 + 5x < 29 – 4
5x < 25

Next we see that x is being multiplied by 5, so to get rid of that 5, we must divide each side by 5:

5x < 25
5x/5 < 25/5
x < 5

Make sense?
 
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