If sec θ + tan θ = x, write the value of sec θ − tan θ in terms of x.

Given: $\sec \theta+\tan \theta=x$

We know that,

$\sec ^{2} \theta-\tan ^{2} \theta=1$

Therefore,

$\sec ^{2} \theta-\tan ^{2} \theta=1$

$\Rightarrow \quad(\sec \theta+\tan \theta)(\sec \theta-\tan \theta)=1$

$\Rightarrow \quad x(\sec \theta-\tan \theta)=1$

$\Rightarrow \quad(\sec \theta-\tan \theta)=\frac{1}{x}$

Hence, $\sec \theta-\tan \theta=\frac{1}{x}$