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Algebra / Linear equations in two variables Difficulty: Medium

If the graph of 27 x + 33 y = 297 is shifted down 5 units in the xy-plane, what is the y-intercept of the resulting graph?

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Explanation

Choice A is correct. When the graph of an equation in the form A x + B y = C , where A , B , and C are constants, is shifted down k units in the xy-plane, the resulting graph can be represented by the equation Ax+By+k=C. It's given that the graph of 27 x + 33 y = 297 is shifted down 5 units in the xy-plane. Therefore, the resulting graph can be represented by the equation 27x+33y+5=297, or 27 x + 33 y + 165 = 297 . Subtracting 165 from both sides of this equation yields 27 x + 33 y = 132 . The y-intercept of the graph of an equation in the xy-plane is the point where the line intersects the y-axis, represented by the point 0,y. Substituting 0 for x in the equation 27 x + 33 y = 132 yields 270+33y=132, or 33 y = 132 . Dividing both sides of this equation by 33 yields y = 4 . Therefore, if the graph of 27 x + 33 y = 297 is shifted down 5 units, the y-intercept of the resulting graph is 0,4.

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

Choice C is incorrect. This is the y-intercept of the graph of 27 x + 33 y = 297 shifted up, not down, 5 units.

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