Help again? (algebra)?

Question

i need help im doing something wrong but i don't know what please help me

ok so here is the problem:

-2x + 8y = 14
-2x + 2y = -26

ok so what i did is subtracted since the both have the same sign

and came up with: 6y = 40

and if i Divide each side by 6y i will come up with 6.666666667

which tells me i did some thing wrong

y can't equal 6.666666667


So now what??????

please explain thanks =)

Answer 1

It's never a good idea to use a calculator when solving your solutions. It's always best to leave fractions in their exact form. If your answer is 3pi, you don't multiply 3 and pi on your calculator; you leave it as 3pi. If your answer is sqrt(2), you don't calculate sqrt(2) on your calculator; just leave it alone.

The same thing goes with 40/6. Leave 40/6 as 40/6. Or, if you prefer, reduce the fraction. But never never calculate.
40/6 = 20/3.

-2x + 8y = 14
-2x + 2y = -26

6y = 40, so y = 40/6, or 20/3

To solve for x, multiply the second equation by 4.

-2x + 8y = 14
-8x + 8y = -104

Subtract.

6x = 118
x = 118/6, or 59/3

Therefore
x = 59/3, y = 20/3

And leave it in these forms!!! Do NOT use your calculator.

Answer 2

there is no way in changing the fixed values of the consonants in a simultaneous eqn like this.

Values can be in the form of a recurring decimal 6.66666666666667 like wat u said. in can be a fraction, negative or positive number. if u get recurring decimals like the above, just convert it into a fraction :6 2/3

nothing is wrong if u do not get whole numbers.

-2x + 8y = 14 (Eqn 1)
-2x + 2y = - 26 (Eqn 2)

Eqn 1 - Eqn 2 (bcos -2x - (-2x )=0):
~ 8y - 2y = 14 - (-26)
~ 6y = 14 + 26
~ 6y = 40
~ y = 40/6
~ y = 6 2/3 (6.666666666666666666667)

Then: substitute y = 6 2/3 into eqn 1:
~ -2x + 8y = 14
~ -2x + 8(6 2/3) = 14
~ -2x + (53 1/3 or 53.3333333333333333) = 14
~ - 2x = 14 - 53 1/3 (change sign when u are moving sth across e equal sign)
~ - 2x = -(39 1/3 or - 39.33333333333333333)
~ x = (39 1/3)/-2
~ x = 19 2/3 or 19.66666666666666666667

therefore, x = 6 2/3 and y = 19 2/3

if u want to double check, simply substitute these values into the equation and see if the right hand side is equal to the left hand side.

Good Luck!! :)

Answer 3

Looks right to me. I get 6y = 40, which means y = 40/6, or 20/3. Plug this back in for "y" in either equation and you get 59/3.

I also second what Puggy said about not using the calculator. There's a good reason for this. Calculators only have so much memory to store a number. So when you have something like 6.66666..., the calculator is always going to round it off after eight places or so. This rounding means that there's always a small amount of error on the calculator. The problem with this is that as you keep doing more and more calculations with numbers like this together, your numbers can get less and less accurate because the degree of error keeps building up. So for solving problems like these, it's best to keep things in fractions. They're exact.

Answer 4

(1) -2x + 8y = 14
(2) -2x + 2y = -26

Multiply (2) by -1 to get:
(3) 2x - 2y = 26
Add (3) and (1):
(2x - 2y = 26)
+ (-2x + 8y = 14)
(0x + 6y = 40)
6y = 40
Divide both sides by 6:
y = 6 2/3
Plug into (1):
-2x + 8(6 2/3) = 14
-2x + 53 1/3 = 14
Subtract 53 1/3 from both sides:
-2x = -39 1/3
Divide both sides by -2:
x = 19 2/3
y = 6 2/3

Why can't y equal 6.66666667?

Answer 5

Why can't y = 6.6667?

Another way to approach the question (more complex but gets the same answer...)
Take the second equation first:
-2x + 2y = -26
Divide by 2 to simplify
-x + y = -13
Figure out what X is:
-x = -13 - y
x = 13 + y

Now for the first equation:
-2x + 8y = 14
Divide by 2 to simplify
-x + 4y = 7
Plug in the equation for Y found above
-(13+y) + 4y = 7
Do the math
-13-y+4y = 7
3y = 7+13
3y = 20
y = 6.667

(x = 19.6667)

Answer 6

Your going about it all wrong. When you have x and y your going to have 2 answers. In each problem set x = 0 and solve....then set y = 0 and solve.

example. -2x + 8y = 14
-2 (0) + 8y = 14
8y = 14
y = 7/4

Answer 7

It's very possible. But to write it better, 6.6666666...7 is 20/3.

On your calculator, just do 2nd fuction: fraction (the button), and it will make a decimal into a fraction.

Answer 8

The method you have done is absolutely ryt (subtraction) way of solving linear equations you just cant assume X=0....I think u shud check the problem once again....

Answer 9

8y-2x= 14---------1
2y-2x= -26---------2

let us multiply equation 1 by -1
-8y+2x= - 14---------3

Now 2+3 = 2y-2x-8y+2x=-14+(-26)
- 6y= - 40
y= 40/6
y= 6.67
x= 19.68

Answer 10

OK...

Devide each side by 2...

thus,

y = 20/3

and from the equation we had.. I think its must be 6.6666667

but you can use 20/3

Nothing is wrong.. keep going
:)