I need help with math...

[Bacon Boy]

Solve by Elimination

y=0,5x+2
1.5x+y=42

Can I have a step-by-step explanation. I think I have to covert y=0,5x+2 into another format, but i forget how.

 

[Jeremy]

So basically you want to eliminate one of the parts that has a variable, so then you only have to solve one variable to start...

Remember that when you alter the left side (before the equals sign) you can alter the right side the same way and they would still be equal. Example: 2 +2 = 4 -> multiply each side by 3 and the equation still works -> 6 + 6 = 12

So then you just multiply one of the parts (and the other stuff in the equation), so that part is the same as the other...

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Wait a second, as I'm typing this I realized you already have two parts of the equations that can be eliminated without the above step... let me continue....

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y=0.5x+2
1.5x+y=42

So what we want to do now is reorganize the equations so they're in the same order... it makes it easier to see. Let's alter the second equation.

1.5x+y=42 ->subtract each side by 1.5x
y=42-1.5x

OK so now we have:

y=0.5x+2
y=42-1.5x

So look at that, we know y equals these two things. We know that if a=b and b=c then a=c... so let's do that:

0.5x+2 = 42-1.5x -> subtract each side by 2
0.5x = 40 - 1.5x -> add 1.5x to each side
2x = 40 -> divide each side by 2
x = 20

Now we know x = 20 so let's find y by going back to one of the equations.

y=0.5(20)+2
y = 12

If you try it with the 2nd equation you should get the same thing

 

[Bacon Boy]

thanks so much storm! but one thing, i need them in x+y= form.

 

[beehdaubs]

This equation can also be solved by Substitution.....
y=0.5x + 2
1.5x + y = 42

You substitute the Y in the second equation with the Y in the first equation. So it would be:
1.5x + 0.5x + 2 = 42
2x = 40
x= 20

Then plug it in....I just thought that I would point out the substitution method also :3

 

[Bacon Boy]

This equation can also be solved by Substitution.....
y=0.5x + 2
1.5x + y = 42

You substitute the Y in the second equation with the Y in the first equation. So it would be:
1.5x + 0.5x + 2 = 42
2x = 40
x= 20

Then plug it in....I just thought that I would point out the substitution method also :3

i know, and graphing, but i need to do it in elimination.

 

[Jeremy]

thanks so much storm! but one thing, i need them in x+y= form.

erm.... what you mean? xD

 

[Bacon Boy]

thanks so much storm! but one thing, i need them in x+y= form.

erm.... what you mean? xD

instead of graphing form, (y=x+b) I need it in x+y=b

 

[Jeremy]

Well if you have y=x+b you can change it to the other one easily, but you're saying they want an equation instead of solving x and y?

 

[Bacon Boy]

they want me to solve for x and y
but it has to be in x+y=b format
like 1.5+y=42
not
y=0.5x+2

 

[Jeremy]

When? You mean before you solve for y and x?

 

[Bacon Boy]

yes