Question at-how
At how many points do the graphs of the equations and intersect in the xy-plane?
At how many points do the graphs of the equations y = x + 20 and
Hard-difficulty · SAT Math · Systems of Two Linear Equations — Graphical solution of two lines. 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. Each given equation is written in slope-intercept form, , where is the slope and is the y-intercept of the graph of the equation in the xy-plane. The graphs of two lines that have different slopes will intersect at exactly one point. The graph of the first equation is a line with slope . The graph of the second equation is a line with slope . Since the graphs are lines with different slopes, they will intersect at exactly one point.
Choice A is incorrect because two graphs of linear equations have intersection points only if they are parallel and therefore have the same slope.
Choice C is incorrect because two graphs of linear equations in the xy-plane can have only , , or infinitely many points of intersection.
Choice D is incorrect because two graphs of linear equations in the xy-plane can have only , , or infinitely many points of intersection.
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