Difficulty: Easy
Correct Answer: 3 : 1 and 1 : 2
Explanation:
Introduction / Context:This problem asks for the ratio x : y that satisfies a homogeneous quadratic relation 2x^2 − 7xy + 3y^2 = 0. Because every term carries the same total degree, dividing through by y^2 (assuming y ≠ 0) reduces the equation to a quadratic in the single variable r = x / y. Solving that quadratic yields the admissible ratios, which must be presented as exact pairs x : y.Given Data / Assumptions:
Concept / Approach:Introduce r = x / y. Divide the equation by y^2 to obtain a standard quadratic in r. Solve using the quadratic formula and convert each r back into the ratio x : y = r : 1 (and, if r is a fraction p/q, express as p : q).Step-by-Step Solution:
Let r = x / y. Then 2r^2 − 7r + 3 = 0.Discriminant D = (−7)^2 − 4*2*3 = 49 − 24 = 25.r = [7 ± √25] / (4) = (7 ± 5) / 4 ⇒ r = 12/4 = 3 or r = 2/4 = 1/2.Thus x : y = 3 : 1 or x : y = 1 : 2.Verification / Alternative check:Substitute r = 3: 2*(9) − 7*(3) + 3 = 18 − 21 + 3 = 0. Substitute r = 1/2: 2*(1/4) − 7*(1/2) + 3 = 0.5 − 3.5 + 3 = 0. Both satisfy the equation exactly.
Why Other Options Are Wrong:
Common Pitfalls:Forgetting to convert r values to simplified integer ratios, or losing a valid root by factoring incorrectly. Always check both quadratic roots and express as clean ratios.
Final Answer:
3 : 1 and 1 : 2
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