SOLUTION: Find a formula for the linear function given below. The function f has f(9)=-39 and f(16)=-81 f(x)= i have no clue how to find a formula for the function, if you can help

Algebra ->  Linear-equations -> SOLUTION: Find a formula for the linear function given below. The function f has f(9)=-39 and f(16)=-81 f(x)= i have no clue how to find a formula for the function, if you can help       Log On


   

Question 317642: Find a formula for the linear function given below.
The function f has f(9)=-39 and f(16)=-81
f(x)=
i have no clue how to find a formula for the function, if you can help me that would be great!
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Linear functions have the form, y=mx%2Bb
Calculate the slope, m,using the two points, (9,-39) and (16,-81)
m=%28y2-y1%29%2F%28x2-x1%29=%28-81-%28-39%29%29%2F%2816-9%29=-42%2F7=-6
Then use either point to find b.
y=-6x%2Bb
-39=-6%289%29%2Bb
-39=-54%2Bb
b=15
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highlight%28y=-6x%2B15%29