The interval of increase of the function f(x)=x-e^x+tan((2π)/7) is

We have $f(x)=x-e^x+\tan(\frac{2π}{7})$

$⇒f'(x)=1-e^x$

For f(x) to be increasing, we must have

$f'(x) > 0 ⇒ 1 - e^x > 0 ⇒ e^x < 1$

$⇒x < 0.⇒x∈(−∞,0)$