What is the focus and the directrix?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

Which radical expression is a rational number? a. √ 360 b. √ 644 c. √ 225 d. √ 122

Measure a and b and find their sum. how are the angles related?