Equation of the line through points?

Question

Find the equation of the line through points (3, 5) and (8, 15). Write the answer in standard form using only integers.

My Answer:

(15-5)/(8-3)

10/5=2
m=2
y=2x+b
15=2(8)+b
15=16+b
-1=b
y=2x-1

slope = (15-5)/(8-3)=2
y intercept = 0

Teacher comments:
Sorry, but I cannot tell what your answer is. It should be an EQUATION but you have given the slope and then the y intercept in different font colors. This is not what you were asked for. Also, minus 1 for no solution checking of the two given points in your eqation.

Answer 1

y = 2x-1 is correct, but it's not in standard form. It's in slope-intercept form. Standard form is ax + by = c. (NOT ax + by + c = 0, see the sourced link for confirmation).

In standard form, your equation would be 2x - y = 1.

Your slope is 2, but your y-intercept is not 0. It's -1.

Your teacher is right about one thing... you do need to read the instructions! Yeah, it seems picky, but it's a good habit to develop, and it'll pay off in the long run.

Answer 2

You had the y=2x-1 earlier, but it's not what you put as your final answer, so she probably didn't see it. Just plug in 5 and fifteen for y and x and then 3 and 8 and make sure it works out.

Answer 3

Standard form means it must be written in the format:
ax +by +c=0
hence:
2x -y -1=0 is the correct answer