If $\mathrm{f}(\mathrm{x})=2\{\mathrm{x}\}+5 \mathrm{x}$, where $\{\mathrm{x}\}$ is fractional part function…
If $\mathrm{f}(\mathrm{x})=2\{\mathrm{x}\}+5 \mathrm{x}$, where $\{\mathrm{x}\}$ is fractional part function, then $f(-1.4)$ is
8.2
-8.2
-5.8
-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 $f(x)=2\{x\}+5 x$
$\therefore \mathrm{f}(-1.4)=2(0.6)+5(-1.4)=-7+1.2=-5.8$