Could you please explain SAT Past paper 3, section 4, question 12? I don’t really understand why the double root is considered a ‘distinct’ zero.
Thank you for your time!
Sure. Would it make you feel better if “distinct” were replaced with “unique”? Those terms are interchangeable here.
When the question says the function has “five distinct zeros,” that really just means there are five values that 1) don’t equal each other, and 2) make the function equal zero.
In other words, f(a) = 0, f(b) = 0, f(c) = 0, f(d) = 0, and f(e) = 0 for unique values a, b, c, d, and e.
In OTHER other words, the function f touches the x-axis five times. Sidestepping all of the above, all you really need to do is count the number of times each graph touches the x-axis.
Choices A and B touch the x-axis four times, and choice C touches the x-axis six times. Only choice D touches it five times.