Question x-y-k-

1.3 Linear Equations in Two Variables - Intercepts and slope applications
0:00
x y
k 13
k + 7 -15

The table gives the coordinates of two points on a line in the xy-plane. The y-intercept of the line is k-5,b, where k and b are constants. What is the value of b ?

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x y k 13 k + 7 - 15 The table gives the coordinates of two

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 33 . It’s given in the table that the coordinates of two points on a line in the xy-plane are (k,13) and (k+7,-15). The y-intercept is another point on the line. The slope computed using any pair of points from the line will be the same. The slope of a line, m , between any two points, x1,y1 and x2,y2, on the line can be calculated using the slope formula, m=y2-y1x2-x1. It follows that the slope of the line with the given points from the table, (k,13) and (k+7,-15), is m=-15-13k+7-k, which is equivalent to m=-287, or m=-4. It's given that the y-intercept of the line is (k-5,b). Substituting -4 for m and the coordinates of the points (k-5,b) and (k,13) into the slope formula yields -4=13-bk-k-5, which is equivalent to -4=13-bk-k+5, or -4=13-b5. Multiplying both sides of this equation by 5 yields -20=13-b. Subtracting 13 from both sides of this equation yields -33=-b. Dividing both sides of this equation by -1 yields b=33. Therefore, the value of b is 33 .