Question

Write an equation in slope-intercept form of the line with the given slope and point: slope = 3 and (1, -2).

Answer 1

Hello there! I can help you out. Do you have any idea where to start with this, or are you completely lost?

Answer 2

im completely lost!

Answer 3

That's perfectly fine :) The thing about math is you really have to get those formulas down, know what I mean? :) That being said, you should really get the formula for this problem memorized because teachers are going to be drilling you with it for a while!

Here's the equation you need for slope-intercept form:

y = mx + b

where "m" is the slope of the line and "b" is the y-intercept. Does this make sense so far?

Answer 4

yes

Answer 5

Okay, good. So now you can start plugging in the variables for your problem.

y = mx + b

Well, they gave you the slope, right? So which variable (letter) would you take out and replace with your slope (3)?

Answer 6

the m would be 3. so y = 3x + b

Answer 7

Perfect! Okay, so do you know what your y intercept would be?

Answer 8

its -2 right?

Answer 9

Yes! Perfect :)

Answer 10

-2= 3x + b

Answer 11

oh ok

Answer 12

I have one more question. That i need some help on. Could you help me real fast please?

Answer 13

Write the slope-intercept form of the equation parallel to y = 7x + 2, which passes through the point (1, -3).

Answer 14

WAIT! I overlooked something very important. I was thinking of another slope formula (see why I said to make sure to keep your formulas in order? *sheepish grin*). Take it back to when you wrote "-2= 3x + b" You were correct in writing it like that. There are a few more steps to take once you reached that point.

Answer 15

ok

Answer 16

-2= 3x + b

is still following the y = mx + b thing. You've plugged in m(slope), you've plugged in your y-int (-2) and now you have to plug in your x-intercept. What should your equation look like now?

Answer 17

-2 = 3x + 1?

Answer 18

No. We're solving for b. (But that was a good guess.) This is what we're looking for:

-2x = 3(1) +b

Do you understand why the equation looks like this?

Answer 19

yeah but why did we add an x to the -2?

Answer 20

Oops, my mistake. Ignore that. :>

Answer 21

-2 = 3(1) + b

Answer 22

Now... Could you solve for b?

Answer 23

would it be 3?

Answer 24

Hmm, not sure how you got that....

-2 = 3(1) + b [so, multiply 3 * 1]

-2 = 3 + b [simplified]

Now you have to solve for b, which means you want b to be by itself. So you would have to add -3 to both sides (so you cancel 3 out, and get b alone on one side of the equation). Make sense?

Answer 25

umm.. not really?

Answer 26

That's okay! :) I'll show you what I mean. First, we have to cancel out this 3 over here by the b....

-2 = 3 + b <------- we don't want 3 over here. We're solving for b, so this 3 is crowding b's space, popping its bubble. :) We have to move it to the other side of the equation, next to -2, which doesn't mind having a buddy right now. :)

(-3 - 2) = (3 - 3) + b <--- We get rid of that 3 by adding it to -3, on BOTH SIDES. On the 'b' side: When you add a negative 3 and a positive 3 together, it makes zero (it cancels out). And you also add -3 to -2, because whatever you do to one side, you do to the other. So your equation will look like this:

-5 = 0 + b

which is another way of saying:

-5 = b

Yes?

Answer 27

Yes! :)

Answer 28

Great! Now we can finally plug 'b' in our equation from earlier.

y = mx + b

We got the slope, and now we FINALLY know the y-intercept (b). So our equation should look like?

Answer 29

y = 3x + 2

Answer 30

Well, we just found out that "b" equals -5.

y = mx + b.....

y = 3x - 5

Do you get this?

Answer 31

ohhhhhhh...... lol i see know!

Answer 32

Excellent! Here's a list of the steps we went through, so you can see it easier. This might help later when you have other problems like this.

y = mx + b, given slope = 3, point (1, -2)

1.) Plug in the slope: y = 3x + b

2.) Plug in the x- and y-intercepts (of the point given): -2 = 3(1) + b

3.) Simplify: -2 = 3 + b

4a.) Get 'b' alone on one side: (-3 - 2) = (3 - 3) + b

4b.) Simplify: -5 = b

5.) Plug 'b' into your equation (this is your final answer): y = 3x - 5

Does this help?

Answer 33

thanks so much!

Answer 34

You're welcome! So did you need help on that other equation now? If so, could you please make another post? This one is getting rather long.

Answer 35

yeah!

Answer 36

Okay :)