Math Is Fun Forum

SlowlyFading

Member

Registered: 2012-06-12

Posts: 149

Standard Form of an Equation and Simplifying fractions!

I just need some help finding the intercepts in this problem. Except this one has a fraction and I don't know how to deal with it if it has a fraction.

This is the question:
5. 3x + 3/2y= -9

This is what I did so far for y:
3(0) + 3/2y= -9
0 + 3/2y= -9
3/2y = -9

So first I had to get it down to the 3/2y = -9, so that I can simplify that and get one of my points. However I don't know how to simplify
3/2y = -9. So, I need to simplify that so I have one of my points and then get the other one.

Hopefully this made sense! Thanks!

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

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Standard Form of an Equation and Simplifying fractions!

First multiply both sides by 2 and then divide both sides by 3.

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

SlowlyFading

Member

Registered: 2012-06-12

Posts: 149

Re: Standard Form of an Equation and Simplifying fractions!

3x + 3/2y= -9
3(0) + 3/2y= -9
0 + 3/2y= -9
3/2y = -9
3/2y = -9

Then I multiplied both sides of that fraction by 2 and got 6/4 and then I divided both sides by 3 and got 2/1.

I'm not sure what's next and if what I did so far is correct?

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

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Standard Form of an Equation and Simplifying fractions!

hi SlowlyFading,

No that's not correct.

You have a fraction 3/2 and want to double it.

If you double the top and double the bottom, you haven't changed the fraction! 

6/4 is the same amount because 3 halves is the same as 6 quarters.

To double a fraction just double the top ...... 3x2 / 2 = 6/2 = 3

Think about it.  you had 3 halves ... that's one and a half .... you double that to get three.

And you need to double the -9 too.  So you should have

3y = -18

Now divide by 3

y = -6

So the interecept is (0,-6)

To find where the line crosses the other axis, put y = 0

3x = -9

so x = -3

The point is (-3,0)

Now, I could stop there, but let's see the graph and check those answers by looking at another point.

My diagram shows I've plotted (0,-6) and (-3,0) and drawn the line.

Then I looked for another point.  I chose (-5,4)

Substitute those numbers into the original equation

3x + 3/2 y = 3 times -5 + 3/2 times 4 = -15 + 6 = -9.  That's what I should get so I think I've got the right points and line.
Bob

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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
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Standard Form of an Equation and Simplifying fractions!

Hi Bob

Is that the MIF Graph Plotter? And if it is, then how did you get it to plot points?

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Standard Form of an Equation and Simplifying fractions!

No.  I did that in Sketchpad.

Bob

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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
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

SlowlyFading

Member

Registered: 2012-06-12

Posts: 149

Re: Standard Form of an Equation and Simplifying fractions!

Thanks Bob Bundy!

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

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Standard Form of an Equation and Simplifying fractions!

You're welcome.

Bob

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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
Sometimes I deliberately make mistakes, just to test you!  …………….Bob