Question the-li

1.3 Linear Equations in Two Variables - Writing equations from data/points
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  • The line slants gradually down from left to right.
  • The line passes through the following points:
    • (negative 8 comma 4)
    • (0 comma 2)
    • (8 comma 0)

The graph of y=fx+14 is shown. Which equation defines function f ?

A.

fx= - 1 4 x - 12

B.

fx= - 1 4 x + 16

C.

fx= - 1 4 x + 2

D.

fx= - 1 4 x - 14

The line slants gradually down from left to right. The line passes through the following points:

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. An equation for the graph shown can be written in slope-intercept form y = m x + b , where m is the slope of the graph and its y-intercept is 0,b. Since the y-intercept of the graph shown is 0,2, the value of b is 2 . Since the graph also passes through the point 4,1, the slope can be calculated as 1-24-0, or - 1 4 . Therefore, the value of m is - 1 4 . Substituting - 1 4 for m and 2 for b in the equation y = m x + b yields y=-14x+2. It’s given that an equation for the graph shown is y=fx+14. Substituting fx+14 for y in the equation y=-14x+2  yields fx+14=-14x+2. Subtracting 14 from both sides of this equation yields fx=-14x-12.

Choice B is incorrect and may result from conceptual or calculation errors.

Choice C is incorrect and may result from conceptual or calculation errors.

Choice D is incorrect and may result from conceptual or calculation errors.