for people who have passed algebra 1 and still remember it...?

Question

solve by elimination:

4x - 9y = 61
10x + 3y = 25

i added them and got:

14x - 6y = 86

how do i solve for x and y? or did i add wrong or something? HELP!!!! thanks. whoever knows how to do it and explains it to me gets 10 points!!!

Answer 1

Multiply the second equation by 3 and then add the equations (that way the y's will cancel).
4x - 9y = 61
30x + 9y = 75
34x = 136
x = 136/34
x = 4
Now plug 4 in for x to either equation.
4(4) - 9y = 61
16 - 9y = 61
-9y = 45
y = -5
Answer: (4,-5)

Answer 2

First Equation:

4x - 9y = 61
10x + 3y = 25 multiply by 3

4x - 9y = 61
30x + 9y = 75 now add them together

34x = 136 solve for x by dividing both sides by 34
x = 4

plug 4 into either equation to solve for y

4(4) - 9y = 61 and solve for y
16 - 9y = 61 subtract 16 from both sides
- 9y = 45 divide both sides by -9
y = 5

answer x = 4, y = -5 or (4,-5)

Check your work by putting your answer back into your equation:

4(4) - 9(-5) = 61
16 + 45 = 61
61 = 61

Answer 3

What you want to do is to multiply one of the equations so that when you add the two one of the variables cancels out. For example, in the first equation we have -9y and in the second equation we have 3y. If we multiply the 2nd equation by 3 then we will get 9y, and the -9y from the first equation plus the 9y from the second equation = 0. It works like this:

4x - 9y = 61
10x + 3y = 25

now multiply the 2nd equation by 3:

4x - 9y = 61
30x + 9y = 75

now add the two together:

34x = 136

therefore x = 4.

Now plug in x=4 into one of your equations to solve for y:
10x + 3y = 25
40 + 3y = 25
3y = -15
y = -5

therefore you have x = 4 and y = -5

Answer 4

Multiply everything in the second equation by 3, then you problem is:
4x - 9y = 61
30x + 9y = 75
Now add them together and you will get:
34x = 136
That was ELIMINITING the y's. Noy divide each side by 34 and you get:
x = 4
Now, go back to the original problem:
4x - 9y = 61
And plug in 4 for x:
4(4) - 9y = 61
Multiply:
16 - 9y = 61
Subtract 16 from both sides:
- 9y = 45
Divide by - 9:
y = -5
So,you answer is (4, -5), that is, x=4 and y= -5.
Hope this helps!

Answer 5

By elimination, they mean multiply one of the equations by something so that when you add them together, one of the variables will equal zero. I would multiply (10x + 3y = 25) by 3. Then you will have:
4x - 9y = 61
30x + 9y = 75
Then when you add the equations, you get 34x = 136.
Solve for x, then use x to find y.

Answer 6

multiply the second equation by 3, then add them.

4x-9y=61
30x+9y=75

so you get
34x=136

solve for x to get 4.

plug this into one of the original equations get

16-9y =61

solve for y to get -5

check your work

4(4) - 9(-5)=16+45=61

10(4) + 3(-5) =40-15=25

hope this helps.

Answer 7

Use substitution.

Take 4x - 9y = 61
4x = 9y + 61
x = (9y+61) / 4

Now take 14x - 6y = 86
14 [(9y+61)/4] - 6y = 86
And solve for y. (I'm too lazy to solve for it myself.)

After you get the number for y, plug it into the equation 4x = 9y + 61 and solve for x.

I just realized you were supposed to solve by elimination. Ah well, you can still use substitution to double-check your answer.

Answer 8

to solve by elimination, you want to get rid of one of the variables. one approach would be to multiply both sides of the second equation by 3 to get:
30x+9y=75

then add them to get

34x = 136

divide both sides by 34 to get
x = 4

then substitute 4 in for the variable x in either equation
4(4) - 9y = 61
16 - 9y = 61 then subtract 16 from both sides
-9y = 45 then divide by -9
y = -5

Answer 9

multiply the bottom equation thru by 3.

That makes it now 30x + 9y = 75.

Now try adding the two equations....

Answer 10

Multiply the second equation by three and then do the elimination from there