The interval of increase of the function $f(x)=x-e^x+\tan (2 \pi / 7)$, is |
(a), (c) (a), (d) (b), (c) (b), (d) |
(b), (d) |
We have, $f(x)=x-e^x+\tan \left(\frac{2 \pi}{7}\right) \Rightarrow f^{\prime}(x)=1-e^x$ For f(x) to be increasing, we must have $f^{\prime}(x)>0 \Rightarrow 1-e^x>0 \Rightarrow e^x<1 \Rightarrow x<0 \Rightarrow x \in(-\infty, 0)$ |