Describe the surface in r3 represented by the equation x + y = 7.

This is a plane in 3D space (aka "3-space") which is like a flat sheet of a paper that doesn't bend at all, and it extends infinitely in all directions along the flat surface. This plane is tilted and not vertical or horizontal. 

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.