Question

Devon wants to write an equation for a line that passes through 2 of the data points he has collected. The points are (8, 5) and (–12, –9). He writes the equation 7x – 10y = 3. Is this a good model? Explain your reasoning.

Answer 1

The points do not make the equation true.

The correct equation in standard form is

7x – 10y = 6.

The y-intercept should be –3/5.

Explanation:

sample response

Answer 2

If the model is good, then both points will check in the equation. Substituting 8 for x and 5 for y in the equation results in 56 – 50 = 3, which is not true. Therefore, the model is not good. Using (–12, –9) as a check results in –84 + 90 = 3. The constant value in the equation should be 6, not 3. In slope-intercept form, the y-intercept should be –3/5.