If the representation is a graph then use the vertical line test. Draw or imagine straight vertical lines going down the graph. If the vertical line only goes through the function line one time then it is a function. For an example, a circle on a coordinate plane is not a function but a wavy line is. If the representation is a table with points then look at the x values. If x repeats then it is not a function.
<span>Let the major axis = 2a , and the minor axis = 2b ∴ a = 26/2 = 13 and b = 24/2 = 12 and the equation of foci: c² = a² - b² = 13² - 12² = 169 - 144 = 25 ∴ c = √25 = 5
∴ The distance between the foci = 2 * 5 = 10 </span>
