SAT Math · Systems of equations in two variables · medium
The graphs of y = x² - 3 and y = 4x - 3 intersect at two points. What is the product of the x-coordinates of these two points?
The graphs of and intersect at two points. What is the product of the -coordinates of these two points?
Answer and explanation
Answer: C: 0
Set the two expressions for equal: . Add 3 to both sides and subtract : , which factors as . The intersections are at and , and the product of the -coordinates is , choice C. Vieta's formulas agree: the product of the roots is the constant term, which is 0. Choice A (4) is the sum of the roots, or the nonzero root. Choice B () is the constant from the original equations, which cancels. Choice D (3) is the same constant with a sign slip.
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