Can some explain this to me

Question

Let g(x) = x4 – 3x+1. Find g(-2)

Answer 1

Just a note: "You simply plug in the number for x wherever you see an x"  is not really quite accurate but works for simple numbers.

 

You can see by the above answers that there is an implied parenthesis around each use of x in the function.

 

That way you don't end up with the following paradox:

 

f(x) = x²

 

plug in "2+1" for x

f(2+1) = 2 + 1²   = 2 + 1 = 3

 

but

f(3) = 3²  = 9

 

This happens because the order operations messes things up without the implied parentheses.

 

so f(x) = x²

 

is really interpreted as F(x) = (x)²

 

Answer 2

g(x)  is a function that converts an independent variable, x, into a new value y.

 

the rule for this particular function is

g(x) = x⁴ - 3x + 1

 

g(-2) is the function acting on a specific value of x.  In this case x = -2.

 

you calculate g(-2) by substituting -2 for x in the equation

 

g(-2) = (-2)⁴ - 3(-2) + 1

         = 16 + 6 + 1

         = 23

 

 

Answer 3

You simply plug in -2 anywhere you see x

 

g(x) = x⁴ – 3x+1

        = (-2)⁴ - 3(-2) + 1

        = 16 +6 +1

         = 23