Question 665004
Maybe there was a typo in your textbook.
I have seen errors in high school textbooks, and some online material has even more errors.
 
To make the meaning clear, you need some brackets.
To write a square root on this website, you need to put whatever is inside that square root in brackets.
 
sqrt(7x)={{{sqrt(7x)}}}=(7x)^(1/2)=7^(1/2)x^(1/2) is not  a linear polynomial with degree 1. The exponent on the variable {{{x}}} is {{{1/2}}}.
sqrt(7)x={{{sqrt(7)x}}} is a linear polynomial with degree 1, because the square root only covers the {{{7}}}, forming a {{{sqrt(7)}}} coefficient in front of the variable {{{x}}}, and the variable's exponent is an implied 1.