Answer:
f(8) = 21
Step-by-step explanation:
First, identify the equation of the line using the form: f(x) =mx + c, where m is the gradient and c is the y-intercept (the constant)
To find gradient, use the rise over run formula: (y2 - y1)/(x2 - x1)
You can use any points but I am going to use (2,3) and (3,6)
(6 - 3)/(3 - 2)
3/1 = 3 (gradient of the graph is 3)
Hence the equation is simplified to: f(x) = 3x + c
Now we need to find the value for c. To do this, you sub in any point, and I am going to use (3,6)
6 = 3*(3) + c (rearrange it to make c on its own)
6 - 9 = c
c = -3
Hence the equation of the line is: f(x) = 3x - 3
So we are trying to figure out what f(8) equals. That means we sub in the value 8 where x is.
3*(8) - 3 = 21
f(8) = 21
