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# Functions Question!!

Given then equation f(x)=-6x-2, determine f(4)

Evaluate f(-2) for the function f(x)= 4x squared-x+5

### 2 Answers by Expert Tutors

Jose S. | Friendly Mathematics, Philosophy, and Computer Science tutorFriendly Mathematics, Philosophy, and Co...
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A function is a rule that you apply to a variable.  In this case the variable,x, represents a number and the rules just tells you what to do with the number.  For f(4), you do: 6*(4)-2  = 24-2 = 22, so f(4) = 22

Do you think you can do it for the other function?  Remember to substitute the number given (-2) and apply the rule: 4x^2 -x +5

edit: that negative was hard to see:  sorry, though if you follow the steps with the correct value the answer works out
Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
5.0 5.0 (428 lesson ratings) (428)
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The notation f(4) means f(x=4).  So just plug in 4 wherever there is an x:

f(x) = -6x - 2

f(4) = -6(4) - 2

f(4) = -24 - 2

f(4) = -26

For f(x) = 4x2 - x + 5

f(-2) = 4(-2)2 - (-2) + 5

f(-2) = ?