Question in-the

2.2 Nonlinear Equations in One Variable - Quadratic solving (factoring, quadratic formula, completing square)
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x squared, minus a, x, plus 12, equals 0

In the equation above, a is a constant and a, is greater than 0. If the equation has two integer solutions, what is a possible value of a ?

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In the equation above, a is a constant and . If the equation has two integer

Hard-difficulty · SAT Math · Nonlinear Equations in One Variable — Quadratic solving (factoring, quadratic formula, completing square). Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

The correct answer is either 7, 8, or 13. Since the given equation has two integer solutions, the expression on the left-hand side of this equation can be factored as open parenthesis, x plus c, close parenthesis, times, open parenthesis, x plus d, close parenthesis, where c and d are also integers. The product of c and d must equal the constant term of the original quadratic expression, which is 12. Additionally, the sum of c and d must be a negative number since it’s given that a, is greater than 0, but the sign preceding a in the given equation is negative. The possible pairs of values for c and d that satisfy both of these conditions are negative 4 and negative 3, negative 6 and negative 2, and negative 12 and negative 1. Since the value of negative a is the sum of c and d, the possible values of negative a are negative 4 plus negative 3, equals negative 7, negative 6 plus negative 2, equals negative 8, and negative 12 plus negative 1, equals negative 13. It follows that the possible values of a are 7, 8, and 13. Note that 7, 8, and 13 are examples of ways to enter a correct answer.