algebra again =) i really need help with my life...lol...?

Question

alllllrighty. so if i have a substitution problem like this:
4x+3y=13
{
x+y=4

OR this...

y=5-x
{
1=4x+3y

how do i solve it??? can ya'll please explain how to solve these?? i would appreciate it so much!!!! and it'd save me the stupid speech about my math grade lol.... THANK You thank you thank you

Answer 1

4x+3y=13
Then x= 4-y ------- 1
Substituting this value in above equation
4(4-y)+3y=13
16-4y+3y=13 (computing -4y any +3y)
16-1y=13
-1y= 13-16
-1y=-3
y= -3/-1
y=3 Puttting this value in eq 1
x= 4-y
x= 4-3=1
So X=1 and Y-3 put these values in ur eq
4x+3y=13
4x1+3x3=13
4+9=13
13=13
Like this u can solve other equation as well. Having some prob. reply back to me.
Regards
Vishwa Deep

Answer 2

There are two basic ways. I'll use one for each problem above.

1. Elimination method.
4x + 3y = 13
x + y = 4

The idea is to eliminate either x or y by adding or subtracting multiple of the two equations (this is perfectly OK to do).
For instance, to eliminate y we take the first equation minus three times the second equation:
(4x + 3y) - 3(x + y) = 13 - 3(4)
=> (4x - 3x) + (3y - 3y) = 13 - 12
Normally you would skip writing these two lines and go straight to
1.x = 1 => x = 1.
Then substitute this into either equation to find y, e.g. 1 + y = 4 => y = 3. So x = 1 and y = 3.

2. Substitution method.
Here we write one variable in terms of the other from one of the equations, and substitute this into the other equation so we get an equation in one variable only.
y = 5 - x
1 = 4x + 3y

Since we already have y in terms of x from the first equation, substitute this into the second equation:
1 = 4x + 3(5 - x)
= 4x + 15 - 3x
= x + 15
So x = -14. Then y = 5 - x = 5 - (-14) = 19. So x = -14 and y = 19.

Answer 3

When you have two unknowns you have to have two equations. You have that, so you can solve them. Start with the simplest equation each time.
x + y = 4. Your goal is to get one letter by itself on one side. With no numbers or anything. You can do this by subtracting y.
x + y - y leaves you with just x. But if you subtract y from one side of the equal sign you have to subtract it from the other as well. So you have x + y - y on the left and 4 - y on the right. That leaves you with x = 4 - y

Now go to the second equation (that looks harder) and replace the x's with (4 - y). Instead of 4x + 3y = 13 you have
4(4-y) + 3y = 13. Now you can figure out y. 4(4-y) is the same as 16-4y. You still have to add 3y. 16-4y + 3y = 13. That leaves you with 16-y = 13. Now subtract 16 from each side as you try to get y by itself. -y = 13 - 16 or -3 so -y = - 3. You want a postive y, so multiply both sides by -1 and you get y = 3.
You figured out earlier that x = 4 - y. If y = 3 then x = 4 - 3 or 1.

That solved the first two. I'll let you work on the bottom two on your own.

Answer 4

you have to find the point if intersection. if you have a graphing calculator this is easy if not you have to use substitution or addition method. i'll show you addition

1. 4x+3y=13
2. x+y=4

choose one variable and make them the same in both equations. i choose x

2. 4(x+y)=(4)4
4x+4y=16
1. 4x +3y=13 make the x's opposite value so one cancells

1. -1(4x +3y)=(13)-1
-4x-3y=-13
2. 4x+4y=16 add them
y=3

plug y into either original equation

3+x=4
-3 -3
x=1

so the answer is (1, 3)

Answer 5

This looks like a system of two equations with two unknowns. To solve it, you solve one equation for one of the unknowns, and substitute it in the other one.

In the first problem, the second equation is less involved, so it is easier to solve for y or x in that equation. Try solving for y:
x + y = 4
y = 4 - x

We now have y written in terms of x, so we can substitute that expression in the first equation:
4x + 3(4 - x) = 13
4x + 12 - 3x = 13
x + 12 = 13
x = 1

Now we have the numerical value of x, and can substitute in either of the two equations to solve for y. It is easier to use the second one:

1 + y = 4
y = 4 - 1
y = 3

Test the results in the first equation to show that it is correct:
4(1) + 3(3) = 4 + 9 = 13 correct

So the answer is x = 1, y = 3

The second problem works the same way.


This is the whole principle of solving systems of equations, you keep substituting until you finally have one equation with only one type of variable in it. Then you solve this and substitute its value in other equations until all variables have their actual values.

Answer 6

(1) 4x + 3y = 13
(2) x + y = 4
Solve (2) for y:
x + y = 4
(1b) y = 4 - x
Plug (1b) into (1):
4x + 3(4 - x) = 13
4x + 12 - 3x = 13
x + 12 = 13
x = 1
Plug into (1b):
y = 4 - x
y = 4 - 1
y = 3
Answer: (1 , 3)

(1) y = 5 - x
(2) 1 = 4x + 3y
Plug (1) into (2):
1 = 4x + 3y
1 = 4x + 3(5 - x)
1 = 4x + 15 - 3x
1 = x + 15
-14 = x
Plug into (1):
y = 5 - x
y = 5 - (-14)
y = 5 + 14
y = 19
Answer: (-14 , 19)

Hope I helped!
10 points best answer?

Answer 7

oh okay so for the first one

its 4x+3y=13
and then you can put x+y=4----> y=-x+4

put it into the problem..it would look like this
4X+3(-x+4)=13...and then you can just do plan arithmetic.^^ and you would get a number for X..use the X to sub back into the original problem to get Y

Second one

ok so all u have to do is sub..it would look like this
1=4X+3(5-X)..distribute it..and then you will find a value for X..one you get that..put X=___ into y=5-x..and you will find the value for Y

hope this helps..

dont wanna give the whole answer out

Answer 8

1) 4x+3y=13......(1)
x+y=4.................(2)
From equation (2) we get x=4-y
Putting this value of x in eqn. (1),we get,
4(4-y)+3y=13
=>16-4y+3y=13
=>-y=13-16= -3
=> y=3
Putting the value of y in eqn no.2
x+3=4
=>x=4-3=1
Therefore x=1 and y=3 ans.
2)y=5-x....(1)
4x+3y=1...(2)
Putting the value of y given in eqn (1) in eqn. no (2) ,we get
4x+3(5-x)=1
=>4x+15-3x=1
=>x=1-15=-14
Putting the value of x in eqn (1) we get,
y=5-(-14)=5+14=19
Therefore,x= -14 and y=19 ans.
If I have failed to make you understand any step/s in the above solutions,please do not hesitate to send a mail to me through Yahoo Answers and I shall be happy to explain the same to the best of my ability.