Question the-gr

1.3 Linear Equations in Two Variables - Writing equations from data/points
0:00

The graph of the equation a, x plus k y, equals 6 is a line in the xy-plane, where a and k are constants. If the line contains the points with coordinates negative 2 comma negative 6 and 0 comma negative 3, what is the value of k ?

A.

negative 2

B.

negative 1

C.

2

D.

3

The graph of the equation is a line in the xy -plane, where a and k

Hard-difficulty · SAT Math · Linear Equations in Two Variables — Writing equations from data/points. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice A is correct. The value of k can be found using the slope-intercept form of a linear equation, y equals, m x plus b, where m is the slope and b is the y-coordinate of the y-intercept. The equation a, x plus, k y equals 6 can be rewritten in the form y equals, the negative of the fraction a, x, over k, end fraction, plus, the fraction 6 over k. One of the given points, with coordinates 0 comma negative 3, is the y-intercept. Thus, the y-coordinate of the y-intercept negative 3 must be equal to the fraction 6 over k. Multiplying both sides by k gives negative 3 k, equals 6. Dividing both sides by negative 3 gives k equals negative 2.

Choices B, C, and D are incorrect and may result from errors made rewriting the given equation.