Question in-the
In the xy-plane, line k intersects the y-axis at the point and passes through the point
. If the point
lies on line k, what is the value of w ?
In the xy -plane, line k intersects the y -axis at the point and passes through
Hard-difficulty · SAT Math · Linear Equations in Two Variables — Intercepts and slope applications. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
The correct answer is 74. The y-intercept of a line in the xy-plane is the ordered pair of the point of intersection of the line with the y-axis. Since line k intersects the y-axis at the point
, it follows that
is the y-intercept of this line. An equation of any line in the xy-plane can be written in the form
, where m is the slope of the line and b is the y-coordinate of the y-intercept. Therefore, the equation of line k can be written as
, or
. The value of m can be found by substituting the x- and y-coordinates from a point on the line, such as
, for x and y, respectively. This results in
. Solving this equation for m gives
. Therefore, an equation of line k is
. The value of w can be found by substituting the x-coordinate, 20, for x in the equation of line k and solving this equation for y. This gives
, or
. Since w is the y-coordinate of this point,
.
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