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Question: Answered & Verified by Expert
If $f$ is linear function and $f(2)=4, f(-1)$ $=3$, then find $f(x)$.
MathematicsFunctionsJEE Main
Options:
  • A $f(x)=3 x+72$
  • B $f(x)=\frac{x+10}{3}$
  • C $f(x)=10-9 x$
  • D none of these
Solution:
1868 Upvotes Verified Answer
The correct answer is: $f(x)=\frac{x+10}{3}$
Let linear function is $f(x)=\mathrm{ax}+\mathrm{b}$
Given $f(2)=4 \Rightarrow 2 a+b=4$
Also $f(-1)=3 \Rightarrow-a+b=3$
Solving (1) and (2) we get $a=\frac{1}{3}$ and $b=\frac{10}{3}$
Hence, $f(x)=\frac{x+10}{3}$

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