systems of linear equations?

Question

-3x + y = 10
7x + y =20

if you can, can u tell me how you did it?

Answer 1

Well I can give an easier way.

(-1)-3x+y=10

3x-y= -10
7x+y=20 Add the equations (the y's cancel out)
________
10x=10

x=1

then plug x into the other equation to get y

Answer 2

I'll show you by using the elimination method. You didnt state a preferred method, I like this way the best.

You can pick to eliminate the x's or the y's first. Let's start with the x's. We want to find the LCM for the numbers(coefficients) with the x's, we also have to make sure that one is negative and one is positive. We want to make it so that when we add them, they are eliminated (killed, gone) thats why its called the elimination method.
So you have -3x and 7x , the only number that can be there LCM is 21. Since -3x is already negative lets make that equation the one to be negative. Now the steps to that:

You are going to take the whole first equation -3x+y=10 and multiply the WHOLE equation by 7, because -3*7= -21, so here we go.

7 (-3x+y=10) gives us -21+7y=70.

Now the second equation will be multiplied by 3 because 3*7=21

3 (7x+y=20) gives us 21x+3y=60.

Take both of your new equations and set them up over each other like this.


-21+7y=70 add the 7y+3y add the 70+60
21x+3y=60

-------------
.......10y=130

now divide both of the numbers by 10 to solve for y


10y/10=130/10

y=13 Now you know what y equals.

Go back to your original equation and pick one. I am going to use the bottom one.

7x + y =20 Now plug in what y equals

So you have 7x+13=20 subtract the 13 from the 13 and the 20
..........................-13 -13
..______________________
.....................7x =7 Now divide them both with 7 to find x


7x/7 7/7

x=1

Your solution set is (1,13)
if you need more help feel free to e-mail me. To check this you can plug x and y into your original equation and solve it.

Answer 3

One way is to make y the subject in both and then put y=y and solve for x. Once x is solved then solve for y.

-3x+y=10 form here y=10+3x ---------------1
7x+y =20 from here y= 20- 7x --------------2

y = y
10+3x = 20-7x
3x+7x = 20-10
10x = 10
x = 1

Now substitute the value of x=1 in either of the 2 equations and find y

y= 10+3(1)
y =13

Answer 4

x = 1

y = 13

Use substitution ..


-3x + y = 10
y = 10 + 3x

7x + 10 + 3x = 2-

10x + 10 = 20
10x = 10
x = 1

Now substitute x in any of the above equationz !!

Answer 5

is it the y=mx+b?

-3x+y=10 switch the -3x to +3x then put it in the other side
y= 3x+10

7x+y=20 switch the 7x to -7x then put it in the other side
y=-7x+20


when u switch
- turns +
+turns -
/ turns x
x turns /

Answer 6

allen slope intercept has nothing to do with this problem...