Question

a line of best fit is f(x)= - 0.86x + 13.5 for the set of points in the table. using the equation for the line of best fit, what is a good approximation for the value of the function, f(x), when x = 18?
\begin{tabular}{|c|c|}hline$x$&$f(x)$\hline2&12\hline3&10\hline5&10\hline6&8\hline7&9\hline8&5\hline9&6\hlineend{tabular}
-5\\
-2\\
3\\
12

Explanation:

Step1: Substitute x value

Substitute $x = 18$ into $f(x)=- 0.86x + 13.5$.
$f(18)=-0.86\times18 + 13.5$

Step2: Calculate multiplication

Calculate $-0.86\times18=-15.48$.
$f(18)=-15.48 + 13.5$

Step3: Calculate addition

$f(18)=-1.98\approx - 2$

Answer:

-2