Question

A line has a slope of -1/7. It passes

through the points (1,2) and (3,y).
What is the value of y?

Answer 1

Let's find y

`\\ \sf\longmapsto m=(y_2-y_1)/(x_2-x_1)`

`\\ \sf\longmapsto (-1)/(7)=(y-2)/(3-1)`

`\\ \sf\longmapsto (-1)/(7)=(y-2)/(2)`

`\\ \sf\longmapsto -2=7y-14`

`\\ \sf\longmapsto 7y=12`

`\\ \sf\longmapsto y=12/7`

Answer 2

y = 12/7

Explanation:

Slope = (change in Y) / (change in x)

-1/7 = (y - 2) / (3 - 1)

-1/7 = (y - 2)/2

Cross multiply: -1(2) = 7(y - 2)

-2 = 7y -14

-2 + 14 = 7y

12 = 7y

12/7 = y