Exercise 18 Page 65

To evaluate a function for a certain value of $x$ means that we substitute the given value for every instance of $x.$ Let's do this for the given function when $x=\text{-}5.$

$f(x)=\text{-}\frac{2x+1}{3}$

Substitute

$x=\text{-}5$

$f(\text{-}5)=\text{-}\frac{2(\text{-}5)+1}{3}$

MultPosNeg

$a(\text{-}b)=\text{-}a\cdot b$

$f(\text{-}5)=\text{-}\frac{\text{-}2\cdot 5+1}{3}$

Multiply

Multiply

$f(\text{-}5)=\text{-}\frac{\text{-}10+1}{3}$

AddTerms

Add terms

$f(\text{-}5)=\text{-}\frac{\text{-}9}{3}$

CalcQuot

Calculate quotient

$f(\text{-}5)=\text{-}(\text{-}3)$

NegNeg

$\text{-}(\text{-}a)=a$

$f(\text{-}5)=3$

When $x=\text{-}5,$ the function's value is $3.$ The ordered pair that corresponds to this result is $(\text{-}5,3).$