Question 133421: OK. i really need help here. Thank you all so much.
Why does the inequality sign change when both sides are multiplied or divided by a negative number? Does this happen with equations? Why or why not? Write an inequality for your class to solve. In your inequality, use both the multiplication and addition properties of inequalities. Explain how you arrived at your answer.
OMG..i need help. please.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Why does the inequality sign change when both sides are multiplied or divided by a negative number?
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Draw a number line.
Put a dot at x = 2 and at x = 10
Notice that 10 is to the right of 2 which means 10 > 2
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Multiply both by -1 to get -2 and -10.
Put those points on the same number line.
Notice that the -10 is to the left of -2 which mean -10 < -2
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That is why you must change the inequality sign when you multiply
by a negative; dividing by a negative is the same as multiplying
by a negative fraction.
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Does this happen with equations? Why or why not?
Yes, the same thing happens with equations; the inequality sign switches.
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Write an inequality for your class to solve. In your inequality, use both the multiplication and addition properties of inequalities. Explain how you arrived at your answer.
-2x +7 < 10
Subtract 7 from both sides to get:
-2x < 3
Divide both sides by -2 to get:
x > -3/2
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Cheers,
Stan H.
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