SOLUTION: Give the equation of the linear function, f(x) if f(1) = 4 and f(3) = 8

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Question 159464: Give the equation of the linear function, f(x) if f(1) = 4 and f(3) = 8
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
A linear equation has the form,
f%28x%29=mx%2Bb
Let's use the values you provide and solve for m and b.
First value,
f%28x%29=mx%2Bb
4=m%281%29%2Bb
1.m%2Bb=4
Second value,
f%28x%29=mx%2Bb
8=m%283%29%2Bb
2.3m%2Bb=8
Subtract eq. 1 from eq. 2,
3m%2Bb-%28m%2Bb%29=8-4
2m=4
m=2
From eq. 1,
1.m%2Bb=4
2%2Bb=4
b=2
The linear equation is,
f%28x%29=2x%2B2