NEED MATH HELP!

[razorshark]

ok, so I'm down to the last two problems and I can't figure these out. If I get these right, I have enough points to pass the class even if I bomb the final, can someone help me out please...

Solve by any method, a&b represent nonzero constants
ax+by=2
-ax+2by=1

so this is what I came up with: {a,b}

next...

6x+5y=-7
-6x+11y=1

I got this: {-41/48,-3/8}...but its not right.

need this pretty quick, thanks

- Sharky

 

[BigBSBusa]

So you're solving for a&b or x&y?

ax + by = 2
-ax + 2by = 1

by = 2 - ax
-ax + 2 (2 - ax) = 1
-ax + 4 - 2ax = 1
-3ax + 4 = 1
-3ax = -3
ax = 1

ax + by = 2
1 + by = 2
by = 1

Then fill in a and b or x and y.

 

[Busa Jules]

I'm a science teacher.. so not a lot of help.... but I sent it to all of the math/ algebra teachers to see what we can do for you!

 

[99'busa]

im getting a headache looking at it but i cant wait to see how long this takes

 

[Busa Jules]

Ditto what big BS said.... I just worked it out (I think) and by = 1 and ax = 1

 

[razorshark]

So you're solving for a&b or x&y?  

ax + by = 2
-ax + 2by = 1

by = 2 - ax
-ax + 2 (2 - ax) = 1
-ax + 4 - 2ax = 1
-3ax + 4 = 1
-3ax = -3
ax = 1

ax + by = 2
1 + by = 2
by = 1

Then fill in a and b or x and y.

Solving for X & Y...x=?, y=?
so is the answer {a,b}, {1,1}, (1a,1b}?

i only have one chance to get this right, and I REALLY need it bad...thanks for your help

 

[Aquaman]

Algebra never made any sence to me at all...

 

[dinoap]

I think I wish the org would go down again like last night, it appears it has been taken over by NASA.org. I feel really dumb right now, I need a nap.

 

[BUSA_CHeMiST]

Ok, see if this makes sense...

Ax + By = 2
-Ax + 2By = 1

Solve for X and Y....
using the top equation...

Ax = 2 - By

Plug this into bottom equation...

-(2 - By) + 2By = 1
-2 + By + 2By = 1
-2 + 3By = 1
3By = 3
y = 1/B

if you work it out, x will be = to 1/A.

So, X = (1/A)
   Y = (1/B)

Plug in some constants to check the work...

we'll use 2 for A and 3 for B

***  2(1/2) + 3(1/3) = 2
***  -2(1/2)+ 2(3(1/3) = 1

 

[BUSA_CHeMiST]

The reason that A and B HAVE to be nonzero constants is because in order for the equation to work out, 1 has to be divided by a NONZERO constant, and as you know im sure, you cannon divide by ZERO.

 

[Busa Jules]

+1 .... what he said.... That is actually what the math teacher just sent to me too!!

 

[BusaWhipped]

... as you know im sure, you cannon divide by ZERO.

Yes you can.  You'll get to that in some of your higher level courses.

 

[razorshark]

Ok, see if this makes sense...

Ax + By = 2
-Ax + 2By = 1

Solve for X and Y....
using the top equation...

Ax = 2 - By

Plug this into bottom equation...

-(2 - By) + 2By = 1
-2 + By + 2By = 1
-2 + 3By = 1
3By = 3
y = 1/B

if you work it out, x will be = to 1/A.

So, X = (1/A)
   Y = (1/B)

Plug in some constants to check the work...

we'll use 2 for A and 3 for B

***  2(1/2) + 3(1/3) = 2
***  -2(1/2)+ 2(3(1/3) = 1

ok, I'm confused now but I got 1/b first, but then back to 1b...damn trick equations...

How positive are you about {1/a,1/b}?

 

[razorshark]

+1 .... what he said.... That is actually what the math teacher just sent to me too!!

cool, thanks...now what about my 2nd problem?

YOU ALL ROCK!

 

[Busa Jules]

Very +++++

 

[BUSA_CHeMiST]

AS far as the next problem goes....

6x + 5y = -7
-6x + 11y = 1

Using the substitution method again...

usin first equation,
subtract 5y from both sides
6x = -7 - 5y

multiply thru by -1 to make this...
(-1)6x = -1(-7 + 5y)
-6x = 7 - 5y

plug into bottom equation...

(7 - 5y) + 11y = 1
SOLVE FOR Y...

7 + 6y = 1
6y = -6
y = -1

go back to top equation and plug -1 in for y and solve for X

6x + 5(-1) = -7
6x = -12
x = -2

SO
x = -2
y = -1

 

[BUSA_CHeMiST]

... as you know im sure, you cannon divide by ZERO.

Yes you can.  You'll get to that in some of your higher level courses.

+1

VERY much later down the road...

and YOU DONT want to go down that road, trust me!

 

[BUSA_CHeMiST]

actully the elimination mehod on that second problem would have been a whole lot quicker..

6x +  5y = -7
-6x + 11y = 1

The 6x and -6x cancel out or "eliminate" if you subtract the two equations...result being...

6y = -6

y = -1

then you can plug y back in either of the original equations and solve for x

6(x) + 5(-1) = -7
6x - 5 = -7
6x = -12
x = -2

 

[razorshark]

ok...first equation answer was correct, thanks again.

But the second one is wrong...its not {-1,-2} or {-2,-1}

 

[BUSA_CHeMiST]

what wsa the correct equations??

6x + 5y = -7
-6x + 11y = 1

?? is that correct?