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 462 . If the first integer is 5 greater than twice the second integer, what is the smaller of the two integers?

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The product of two positive integers is 462 . If the first integer is 5 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

The correct answer is 14 . Let x represent the first integer and y represent the second integer. If the first integer is 5 greater than twice the second integer, then x=2y+5. It's given that the product of the two integers is 462 ; therefore xy=462. Substituting 2y+5 for x in this equation yields (2y+5)(y)=462, which can be written as 2y2+5y=462. Subtracting 462 from each side of this equation yields 2y2+5y-462=0. The left-hand side of this equation can be factored by finding two values whose product is 2(-462), or - 924 , and whose sum is 5 . The two values whose product is - 924 and whose sum is 5 are 33 and - 28 . Thus, the equation 2y2+5y-462=0 can be rewritten as 2y2-28y+33y-462=0, which is equivalent to 2y(y-14)+33(y-14)=0, or (2y+33)(y-14)=0. By the zero product property, it follows that 2y+33=0 or y-14=0. Subtracting 33 from both sides of the equation 2y+33=0 yields 2y=-33. Dividing both sides of this equation by 2 yields y=-332. Since y is a positive integer, the value of y isn't -332. Adding 14 to both sides of the equation y-14=0 yields y=14. Substituting 14 for y in the equation xy=462 yields x(14)=462. Dividing both sides of this equation by 14 yields x=33. Therefore, the two integers are 14 and 33 , so the smaller of the two integers is 14 .