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audio read-through Identifying Inequalities with Variables as True or False

An Inequality that is Always True

Consider the inequality ‘$\,x \lt x + 1\,$’. Let $\,x\,$ be any real number. Then, $\,x+1\,$ lies one unit to the right of $\,x\,$ on a number line. Therefore, $\,x\,$ always lies to the left of $\,x+1\,,$ so the sentence ‘$\,x \lt x + 1\,$’ is always true.

x is less than x+1

An Inequality that is Always False

Consider the inequality ‘$\,x -1> x\,$’. Let $\,x\,$ be any real number. Then, $\,x-1\,$ lies one unit to the left of $\,x\,$ on a number line. Therefore, $\,x-1\,$ never lies to the right of $\,x\,,$ so the sentence ‘$\,x-1 > x\,$’ is always false.

x-1 is less than x

For these exercises, you should think in terms of position on a number line, as in the previous examples.

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Examples

Determine if each inequality is ALWAYS TRUE or ALWAYS FALSE.

‘$\,x-1 \lt x + 1\,$’     is     Always True
‘$\,x \gt x + 2\,$’     is     Always False
Master the ideas from this section by practicing below:

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When you're done practicing, move on to:

Solving Equations of the Form $\,xy = 0$
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Practice

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ALWAYS TRUE
ALWAYS FALSE
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