Question 230577
>Given that f(3)=12 and f(5)=-2 find f(1/7)

>I've tried the f(x)=mx+b formula
Good idea.

>f(3)=m(3)+b=12
>f(5)=m(5)+b=-2
The way you've written this is confusing. It would be better as:
12 = m(3) + b
-2 = m(5) + b

>M=-14/-2
>M=-7
Still good.<br>
Now we just use this value for "m" to find "b". We can substitute into either equation:
12 = (-7)(3) + b
12 = -21 + b
33 = b<br>
So the function is:
f(x) = -7x + 33<br>
And finally we can use this to find f(1/7):
f(1/7) = -7(1/7) + 33
f(1/7) = -1 + 33
f(1/7) = 32