Functions Question!!

Question

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

 

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

Answer 1

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) = ?

Answer 2

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