Question

Points A( − 1, 7), B(2, 19), and C(3, y) are on the same line. Find y.

Answer 1

Answer: y=23

Explanation:

If Points and A,B and C lines on the same line then they will have the same slopes so since we have the coordinates of A and B we will use the to write an equation in slope intercept form.

To write it in slope intercept form we will need to find the slope and the y intercept.

To find the slope you will find the change in the y coordinates and divide it by the change in the x coordinates.

Using the coordinates (-1,7) and (2,19) the y coordinates are 7 and 19 and the x coordinates are -1 and 2.

Slope :
`(7-19)/(-1-2) (-12)/(-3) = 4` In this case the slope is 4 so we will use that to find the y intercept by using point A coordinate.

The slope intercept formula says that y=mx +b where me is the slope and b is the y intercept.

7=4(-1) + b

7 = -4 + b

+4 +4

b= 11 The y intercept is 11.

Now we can write the whole equation as y=4x + 11 .

To answer the question now, where we need to find y , we will plot the x coordinate which is 3 into the equation and solve for y.

y = 4(3) + 11

y = 12 + 11

y = 23