Question the-pr

2.2 Nonlinear Equations in One Variable - Quadratic solving (factoring, quadratic formula, completing square)
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The product of two positive integers is 546 . If the first integer is 11 greater than twice the second integer, what is the smaller of the two integers?

A.

7

B.

14

C.

39

D.

78

The product of two positive integers is 546 . If the first integer is 11 greater

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

Choice B is correct. Let x be the first integer and let y be the second integer. If the first integer is 11 greater than twice the second integer, then x = 2 y + 11 . If the product of the two integers is 546 , then xy=546. Substituting 2 y + 11 for x in this equation results in 2y+11y=546. Distributing the y to both terms in the parentheses results in 2 y 2 + 11 y = 546 . Subtracting 546 from both sides of this equation results in 2 y 2 + 11 y - 546 = 0 . The left-hand side of this equation can be factored by finding two values whose product is 2-546, or -1,092 , and whose sum is 11 . The two values whose product is -1,092 and whose sum is 11 are 39 and -28 . Thus, the equation 2 y 2 + 11 y - 546 = 0 can be rewritten as 2y2+28y-39y-546=0, which is equivalent to 2yy-14+39y-14=0, or 2y+39y-14=0. By the zero product property, it follows that 2 y + 39 = 0 and y - 14 = 0 . Subtracting 39 from both sides of the equation 2 y + 39 = 0 yields 2 y = -39 . Dividing both sides of this equation by 2 yields y = - 39 2 . Since y is a positive integer, the value of y is not - 39 2 . Adding 14 to both sides of the equation y - 14 = 0 yields y = 14 . Substituting 14 for y in the equation xy=546 yields x14=546. Dividing both sides of this equation by 14 results in x = 39 . Therefore, the two integers are 14 and 39 , so the smaller of the two integers is 14 .

Choice A is incorrect and may result from conceptual or calculation errors.

Choice C is incorrect. This is the larger of the two integers.

Choice D is incorrect and may result from conceptual or calculation errors.