Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

I need help finding 2 points from these equations. I tried solving them myself (My work is below) but it was wrong. So I need the correct answers and please show your work. Thank you!

**I need help with this one: 4x + 3y = -15**

**My work for it:**

4x + 3y = -15

4(0) + 3y = -15

0 + 3y = -15

3y = -15

-15/3

(0, -5)

4x + 3y = -15

4x + 3(0) = -15

4x + 0 = -15

4x = -15

-15/4

I got 3.75, so I rounded that up to 4.

(4, 0)

The points are (0, -5) and (4, 0)

**The Equations: y = 2x, x + y = 3 **

y = 2x

y = 2(2)

y = 4

(2, 4)

x + y = 3

First I picked 2 for x.

2 + y = 3

If we subtract 2 from both sides of the equation we will get y by itself.

2 - 2 + y = 3 - 2

2 - 2 = 0 so the left hand side becomes

0 + y = 3 - 2

Now y + 0 is the same as y so the left hand side becomes

y = 3 - 2

Now 3 - 2 = 1 so the right side becomes

y = 1

(2, 1)

I don't think any of the work is wrong but the problem is only one point was found for each equation. I need 2 points from each equation.

I'm just here to get some help with an online math course I'm taking.

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

y = 2x, x + y = 3

Actually, I'm not exactly sure what's wrong with the problem above. Is there even a problem with that one? Do I need more points?

I'm just here to get some help with an online math course I'm taking.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,657

hi SlowlyFading

Your working to get (2,4) and (2,1) is all correct. If you want more points, just choose another value for x, and work out the y values as you have done.

(0,-5) is correct for the first question.

(4,0) is not correct.

Every thing was correct up to

4x = -15

Then it went wrong.

The x coordinate should have been negative.

And I would not have rounded it at all. When you come to draw the graph, the line will not be in the right place.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**debjit625****Member**- Registered: 2012-07-23
- Posts: 101

SlowlyFading wrote:

15/4

I got 3.75, so I rounded that up to 4.

(4, 0)

These coordinates or points are from cartesian coordinate system,they all have different meanings,you just cant change it a bit ,if you do the whole system will go wrong...

In short never round up any point of any coordinate,if the answer is in fraction keep it in fraction

So in this case your coordinate will be

SlowlyFading wrote:

I don't think any of the work is wrong but the problem is only one point was found for each equation. I need 2 points from each equation.

Like you picked 2 for x ,just pick any other number for x you will get another point.

Good Luck

*Last edited by debjit625 (2012-07-27 20:35:53)*

Debjit Roy

___________________________________________________

The essence of mathematics lies in its freedom - Georg Cantor

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

Thanks guys!

How does this work:

x + y = 3

x + 2 = 3

-2 -2

-1/1

(3, -1)

It's the only one I'm not sure about..

I'm just here to get some help with an online math course I'm taking.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 105,656

Hi;

What is (3, -1)?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.****No great discovery was ever made without a bold guess. **

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

The (3, -1) is the point.

I'm just here to get some help with an online math course I'm taking.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 105,656

Hi;

It is certainly not on x + y = 3.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.****No great discovery was ever made without a bold guess. **

Offline

**debjit625****Member**- Registered: 2012-07-23
- Posts: 101

I think you have one equation and solving it will be like this

Let y be 2

Subtract 2 from both the sides

So your point will be

Now let x be 2

Subtract 2 from both the sides

So your point will be

Normally we use intercept to find any two points of a straight line i.e... take x as 0 and solve for the equation and then take y as 0 and solve the equation.

If you take x as 0 then y will be 3

Good Luck

Debjit Roy

___________________________________________________

The essence of mathematics lies in its freedom - Georg Cantor

Offline

**debjit625****Member**- Registered: 2012-07-23
- Posts: 101

SlowlyFading wrote:

The (3, -1) is the point.

This point can't be from the equation

,let substitute the values of x and y in the equation*Last edited by debjit625 (2012-07-30 04:25:39)*

Debjit Roy

___________________________________________________

The essence of mathematics lies in its freedom - Georg Cantor

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

Okay! Thanks. <3

I'm just here to get some help with an online math course I'm taking.

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

And, how exactly do you graph points like that?

I'm just here to get some help with an online math course I'm taking.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,657

see below

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**SlowlyFading****Member**- Registered: 2012-06-12
- Posts: 149

Thanks!

I'm just here to get some help with an online math course I'm taking.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,657

You're welcome.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline