How do i solve a limit as it approaches infinity

[questions77]

I'm only familiar with limits as they approach a number. Thanks

 

[pka]

View attachment 21596

Note that as \(x\to \infty\) then \(\dfrac{1}{x}\to 0\).
\(x-\sqrt{x^2+7x}=\dfrac{-7x}{x+\sqrt{x^2+7x}}=\)\(\dfrac{-7}{{1}+\sqrt{1+\tfrac{7}{x}}}\)