ACT Preparation / Unit 9 ACT 0819 short lesson, about 20 seconds
Inequalities: the Sign Flip
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The idea
A linear inequality is solved like an equation, with one exception: multiplying or dividing both sides by a negative number reverses the inequality sign.
In practice
−3x + 4 > 19 gives −3x > 15, so x < −5.
Where people slip
Test a value: x = −6 gives 18 + 4 = 22, which is greater than 19.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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