21. What is the slope and equation of a line that is perpendicular to the y -axis passing through point (-5, -3)?
A. The slope is zero and the equation of the line is y = -3.
B. The slope is undefined and the equation of the line is y = -3.
C. The slope is undefined and the equation of the line is x = -5.
D. The slope is zero and the equation of the line is x= -5.

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.