It is trivial to show that $$\sqrt {1+2x} < e^x, \quad \text{for}\, x>0$$ Is it true the stronger inequality $$\sqrt {1+\frac{8x}{4-x}} < e^x, \quad \text{for}\, x>0?$$
2026-04-05 10:39:00.1775385540
Inequality involving exponential function
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If $x\ge 0$ then $1+x+\frac12x^2\le e^x$ because the LHS is a truncation of the power series for $e^x$ and the missing terms are positive. Thus if $x\in[0,3]$ then $$ 4+7x \le 4+7x+2x^2(3-x) = (4-x)(1+2x+2x^2) \le (4-x)e^{2x} $$