math help??

Question

2x+5y=3
-x+3y= -7
i need help please show work

Answer 1

isolate "x" or "y" in either equation. let's isolate "x" in the 2nd equation.

First: subtract 3y from both sides (when you move a term to the opposite side, always use the opposite sign).

-x+3y=3y= -7-3y
-x = -7-3y ("x" has to be positive - change each sign).
x = 7+3y

Sec: substitute 7+3y with "x" in the 1st equation.

2(7+3y)+5y = 3
2(7)+2(3y)+5y = 3
14+6y+5y = 3
14+11y = 3 (subtract 14 from both sides).
14-14+11y = 3-14
11y = -11 (divide both sides by 11).
11y/11 = -11/11
y = -1

Third: substitute -1 with "y" in the 2nd equation.

- x + 3(-1) = -7
- x + (-3) = -7
- x - 3 = -7 (add 3 with both sides).
- x - 3 +3= -7+3
-x = -4
x = 4

Solution Set: (4, -1)

Answer 2

2x+5y=3
-x+3y=negative7

Solution 29926

2x + 5y = 3
-x + 3y = -7
------------------- Multiply the entire second equation by 2 (it is easy to eliminate the x here)
2x + 5y = 3
-2x + 6y = -14
------------------- Add the two equations together.
0x + 11y = -11
or
11y = -11
y = -1
Now substitute this value into either of the two original equations...
-x + 3(-1) = -7
-x + (-3) = -7
-x - 3 = -7
-x = -4
x = 4
Your solution is (4, -1)
Here are the steps to what you need to do.
1) See if you can eliminate a variable by adding or subtracting the two equations.
2) If you can't, multiply one, or both, of the equations by a number such that a coefficient of a term in one equation will match the coefficient of a like term in the other equation.
3) Add or subtract the equations.
4) Solve for the variable that was not eliminated.
4) Substitute this new value back into one of the original equations to find the value of the other variable.

Answer 3

I assume the question is to solve this system of equations.

Rewrite one of the equations in terms of either x or y. For example

x = 3y + 7

then substitute into the other equation

2(3y + 7) + 5y = 3
6y + 14 + 5y = 3
11y = - 11
y = -1

thus x = 3(-1) + 7
x = 4

check the solution
2(4) + 5(-1) = 3 (true)
-(4) + 3 (-1) = -7 (true)

Therefore the solution is x=4, y=-1

Answer 4

Solve for X in the second equation. Its easier. Then you'll get X in terms of Y and you can substitute that back into the first equation and get a number for Y.

I won't do your homework for you so here is a similar example.

-2x - 8y = 24
x - 4y = 8

To solve for x you have to add 4y from both sides of the bottom equation. x - 4y + 3y = 8 + 4y. This simplifies to x = 8 + 4y. So now you know that X = 8 +4Y, Whatever X and Y are you know that 4 times Y plus 8 will always = X. Now you can put that into the first equation

-2(8 + 4y) -8y = 24. You can solve that and get a number for y. To solve it you multiply out the -2 into (8 + 4y) to get the equation -16 -8y - 8y = 24 Combine the -8y and -8y to get -16 - 16y = 6. Add 16 to both sides -16 + 16 - 16y = 8 + 16 to get 16y = 32. Divide both sides by 16 to get Y = 2.

So you know Y = 2. And you Know that whatever Y is, X = 4 times Y plus 8. So X = 4(2) + 8. X = 16.

This is called the substitution method and it should be described in your math book.

The number isn't as important as understanding the process is. The same process will help you answer your question. I think this is called the substitution method and it should be discussed in your math book.

Answer 5

2x + 5y = 3
-2x + 6y = -14 (second equation * 2)

11y = -11
y = -1

2x + 5*-1 = 3
2x - 5 = 3
2x = 8
x = 4

Another way to solve

From the second equation,
x = 3y + 7

Plug that into the second equation.

2(3y + 7) + 5y = 3
6y + 14 + 5y = 3
11y = -11
y = -1 and so on.

Answer 6

so simple!

u need to do linear combination!

2x+5y=3
-x+3y= -7

multiply the bottom by 2 in order to cancel out the x's. so

-x+3y= -7 (2)
u get
-2x+6y=-14

add with first equation so
2x+5y=3
-2x+6y=-14 equals

11y=-11

divide by 11 u get -1

plug -1 into origianl simplest equation so

-x+3(-1)=7

solve, u get x= -10

so yr two variables are (-10, -1)

Answer 7

2x+5y=3
-x+3y=-7
3y=x-7 (added X to both sides of second equation)
y = (x-7)/3 (divide both sides by 3... probably not the simplest solution... but I'm going with it because simple is too easy :p )

2x + 5((x-7)/3) = 3 (substituted the modified equation #2 into eqyation #1)

2X + (5x - 35 )/3 = 3

Lets multiply by 3 to clear the denominator...

6X + 5X - 35 = 9
11X = 44
X = 4

Now plug that value of X into the original -x+3y=-7...

-4+3y = -7

3y = -3
y = -1

X=4 Y = -1

Answer 8

multiply the second equation by two

so

2x + 5y = 3
-2x + 6y = -14

add the equations

11y = -11
y = -1

plug it back into the equation
2x + (-5) = 3
2x = 8
x = 4

Answer 9

multiply the second equation by 2 then add the two equations.
2x+5y=3
-2x+6y=-14

11y=-11
extract y. y=-1
2x-5=3
2x=8, x=4
so the solutions are x=4 and y=-1

Answer 10

2x+5y=3 eq.(1)
-x+3y=-7 eq.(2)
Multiply eq.(2) by 2 on both sides
-2x+6y=-14 eq.(3)
Add eq.(1) & eq.(3)
11y=-11
y=-1
put this value of y in eq.(2)
-x-3=-7
-x=-4
x=4
You can also put value of y in eq.(1) whicever way you feel easy, you will get the same answer for x.