Question

Given a function $f$ such that $f\left(4\right)=5$ , then which of the following is/are true for $f$?

• A. $f\left(x\right)\ne x+1$
• B. $f\left(x\right)\ne 2x-3$
• C. $f\left(x\right)\ne 3x-2$
• D. $f\left(x\right)\ne 4x-11$

Answer 1

Answer: (C)

$f\left(x\right)\ne 3x-2$

(A) $f\left(x\right)=x+1$

Put the value $x=4$, we get

Then, $F\left(4\right)=4+1=5$

(B) $f\left(x\right)=2x-3$

Put the value $x=4$, we get

Then, $f\left(4\right)=2\times 4-3=8-3=5$

(C) $f\left(x\right)=3x-2$

Put the value $x=4$, we get

$f\left(4\right)=3\times 4-2=12-2=10\ne 5$

(D) $f\left(x\right)=4x-11$

Put the value $x=4$, we get

$f\left(4\right)=4\times 4-11=16-11=5$