Question

A family built a house in a beach resort area. In 1990, the house was 430 ft from the water. With erosion, the house was 400 ft from the water in 2000. Assuming a linear relationship between the number of years x since 1990 and the distance y of the house from the water, write an equation for y as a function of x.

Answer 1

The answer on Edgenuity2020 is b. y = -3x + 430

Answer 2

We develop an equation for the given situation by first writing the general equation for lines,
y = mx + b
Substituting to this given the values given above,
(1990) 430 = b
(2000) 400 = m(10) + 430
The value of m from the equation in 2000 is -3. Thus, the equation of that relates the variables is,
y = -3x + 430