Q52 / 150 · MHT CET 2021 (24 Sep Shift 2) · Mathematics

If $\mathrm{f}(\mathrm{x})=2\{\mathrm{x}\}+5 \mathrm{x}$, where $\{\mathrm{x}\}$ is fractional part function, then $f(-1.4)$ is

  • A
    8.2
  • B
    -8.2
  • Correct answer
    C
    -5.8
  • D
    -5

Solution

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 $f(x)=2\{x\}+5 x$ $\therefore \mathrm{f}(-1.4)=2(0.6)+5(-1.4)=-7+1.2=-5.8$

Hence, the correct answer is option: 'C'.

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