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smc

counting and probability senior

Problem

Consider equations of the form . How many such equations have real roots and have coefficients and selected from the set of integers ?
(A)
(B)
(C)
(D)
Solution
The discriminant of the quadratic is . Since the quadratic has real roots, If , then can be from to . If , then can also be from to . If , then can be from to . If , then can be or . If , then can only be . If , no values of in the set would work. Thus, there are a total of equations that work. The answer is .
Final answer
B