Question

The range of the function $f\left(x\right)=5^x+5^{-x}+5$ for $x\in R$ is

• A. $[3,\infty )$
• B. $[5,\infty )$
• C. $[7,\infty )$
• D. $(7,\infty )$

Answer 1

The correct option is C $[7,\infty )$

$f\left(x\right)=5^x+5^{-x}+5$
We know that, $5^x+\frac{1}{5^x}\ge 2$
$\Rightarrow 5^x+\frac{1}{5^x}+5\ge 7$