If f(x)=-3x + 9, then what does f(13)= ?

Question

If f(x)=-3x + 9, then what does f(13)= ?

Answer 1

Hi sophie, to find the value of f(13), all you need to do is replace 13 where ever there is an x in the function.

 

f(x) = -3 * x + 9

 

Replace the x by 13:

 

f(13) = -3 * 13 + 9

 

f(13) = -39 + 9

 

F(13) = 30

 

Questions?

Answer 2

Simply substitute 13 into the equation & solve:

 

f(13)=-3(13)+9 (substitute)

f(13)=-39+9 (distribute/multiply)

f(13)=-30 (add)