saleem.kh wrote:Does the curve (x - a)^2 + (y - b)^2 = 16 intersect the Y axis?
1) a^2 + b^2 > 16
2) a = |b| + 5

I read this question on another forum but couldn't understand explanation of solution. Can anybody help me to solve it.

That solution relies on a knowledge of coordinate geometry far beyond what you need on the GMAT.

In this question, we are asked about y-intercepts. To find y-intercepts, we plug in x=0. So we want to know if there are any solutions to

(0 - a)^2 + (y - b)^2 = 16

a^2 + (y - b)^2 = 16

(y-b)^2 = 16 - a^2

Now, the left side of this equation cannot be negative, since it is a square. So this equation will have no solutions if the right side is negative.

From Statement 1, we have that 16 - a^2 < b^2. So certainly 16-a^2 could be negative, but could also be positive, and we don't know if we have solutions to our equation: not sufficient.

From Statement 2, we know that a = |b| + 5. Since |b| is at least 0, this guarantees that a is at least 5, so we know 16 - a^2 is negative, and the equation (y-b)^2 = 16 - a^2 cannot possibly have a solution. Sufficient - the answer is B.