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Question: Answered & Verified by Expert
If $\mathrm{f}(\mathrm{x})=2\{\mathrm{x}\}+5 \mathrm{x}$, where $\{\mathrm{x}\}$ is fractional part function, then $f(-1.4)$ is
MathematicsFunctionsJEE Main
Options:
  • A 8.2
  • B -8.2
  • C -5.8
  • D -5
Solution:
1902 Upvotes Verified Answer
The correct answer is: -5.8
We know that $\mathrm{x}=[\mathrm{x}]+\{\mathrm{x}\}$
When $\mathrm{x}=-1.4$, we get $[\mathrm{x}]=-2$ and $\{\mathrm{x}\}=0.6$
We have $f(x)=2\{x\}+5 x$
$\therefore \mathrm{f}(-1.4)=2(0.6)+5(-1.4)=-7+1.2=-5.8$

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