Question

write in standard form the equation of each line.
1) slope= 3; (-1,4)

I know standard form is ax+by=c but I have no idea how to even begin solving this problem let alone understand the entire subject please help

Answer 1

y - y1 = m(x - x1) ... start with point slope form

y - y1 = 3(x - x1) ... plug in the given slope

y - 4 = 3(x - (-1)) ... plug in the given point

y - 4 = 3(x + 1)

y - 4 = 3x + 3

y = 3x + 3 + 4

y = 3x + 7

y - 3x = 7

-3x + y = 7

3x - y = -7

Answer 2

Let me know if that helps or not

Answer 3

wait, so y=3x+7
how did you get y-3x=7? @jim_thompson5910

Answer 4

I subtracted 3x from both sides to get y - 3x = 7

then rearranged the equation to get -3x + y = 7

Answer 5

Most books will want a > 0, so I then multiplied every term in -3x + y = 7 by -1 to get 3x - y = -7

Answer 6

Does that make sense?

Answer 7

ok, so for 2) slope= -1; (0,7)
y-y1=m(x-x1)
y-y1=-1(x-0)
y-7=-1x-0
y=7-1x
1x+y=7

Is that right?

Answer 8

1x+y=7 is the same as x+y=7

Answer 9

Let's check that answer

x + y = 7

0 + 7 = 7 ... plug in x = 0, y = 7. This is from (0,7)

7 = 7 ... this is true, so (0,7) definitely lies on this line

Answer 10

And it turns out that x+y = 7 has a slope of -1 because solving for y gives you y = -x + 7

Answer 11

So the answer checks out

Answer 12

I did it! oh my gosh thank you SO much, I was struggling with this subject

Answer 13

Yes you did. Just keep practicing with this and it'll click much smoother. However, it looks that you are already a pro at this. So congratulations with that. Keep up the good work.

Answer 14

thank you so much!

Answer 15

you're welcome