Question at-how

1.4 Systems of Two Linear Equations - Graphical solution of two lines
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At how many points do the graphs of the equations y = x + 20 and y = 8 x intersect in the xy-plane?

A.

2

B.

8

C.

0

D.

1

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, y = m x + b , where m is the slope and 0,b 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 1 . The graph of the second equation is a line with slope 8 . 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 0 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 0 , 1 , or infinitely many points of intersection.

Choice D is incorrect because two graphs of linear equations in the xy-plane can have only 0 , 1 , or infinitely many points of intersection.