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Given f(x)=-4x+8, verify if f(x)>4 then x>1?

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fab10 | Student, Undergraduate | (Level 1) Honors

Posted August 23, 2011 at 8:14 PM via web

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Given f(x)=-4x+8, verify if f(x)>4 then x>1?

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giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted August 23, 2011 at 8:18 PM (Answer #1)

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We'll substitute f(x) by it's equation:

-4x+8 > 4

We'll isolate -4x to the left side subtracting 8 both sides:

-4x + 8 - 8 > 4 - 8

-4x > -4

We'll divide by -4 both sides changing the direction of inequality:

x < 1

We notice that if f(x) > 4, then x < 1, therefore the constraint given by enunciation is not true.

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