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Plug in x = -4 in the inequality -3x +4 19 what is your result? Plug in a number that is greater than your solution? Does it work out the way it's supposed to? Why or

Why not?
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1 Answer

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The original inequality is -3x+4 > 19

Let's replace x with -4 and see what happens.

-3x + 4 > 19

-3(-4)+4 > 19

12+4 > 19

16 > 19

The last inequality is false, so the original inequality is false when x = -4.

This means x = -4 is not a solution to -3x + 4 > 19

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Let's plug in something larger. Let's say x = -3 which is one space to the right of -4 on the number line.

So we get...

-3x + 4 > 19

-3(-3) + 4 > 19

9 + 4 > 19

13 > 19

This doesn't work either. The value x = -3 is not a solution.

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Let's determine which x values will work by solving for x

-3x + 4 > 19

-3x + 4 -4 > 19-4 ... subtracting 4 from both sides

-3x > 15

-3x/(-3) < 15/(-3) ... divide both sides by -3; inequality sign flips

x < -5

The solution set consists of values smaller than -5

So values like {-6, -7, -8, -9, ...} and decimal values as well in that interval.

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