HELP! i don't get my algebra at all! solving equations by elimination mult/add?

Question

solving equations by elimination mult/add

7x + 2y = -1
3x - 4y = 19

first i multiplied everything int he first equation by 3
so i now have 21x+ 6y = -3
and i multiplied everything in the second equation by 7 and got
21x - 28y = 133
then the 21x and 21x cross out
so i now have
6y = -3 and -28y = 130[add 133 and -3]
so next i subtracted 6y from -28y and got -22y = 130
now what? HELP! please!

oh & its supposed to be a coordinate at the end
so you figure out y and then plug it in to find out x

Answer 1

you have this right
21x + 6y = -3
21x - 28y = 133
notice that both eqns. have positive 21x so you need to "add the opposite"
21x + 6y = -3
-21x + 28y = -133 add these
34y = -136
y = -4

use 7x + 2y = -1
7x + 2(-4) = -1
x = 1

answer (1 , -4)
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Answer 2

The start was great. You wanted to get one of the variables to have the same numerical coefficent. You had:

21x + 6y = -3
21x -28y = 133

Now the goal is to get rid of one of the variables. Instead of adding the two equations, lets subtract. So multiply everything in the second equation by -1:

21x + 6y = -3
-21x +28y = -133

Now we get 34y = -136
Divide both sides by 34 and get y = -4

Plug -4 back into one of the original equations, it doesn't matter which one.

7x+2*(-4) = -1
7x-8 = -1
7x = 7
x = 1

Answer 3

21x + 6y = -3
21x -28y = 133
you can't just cross them off. You have to either subtract the two or add the two. In this case I'll subtract the two equations, and I get
0 +34y = -136
y = -136/34 = -68/17 = -4
7x +2(-4) = -1
7x = 7
x= 1

Answer 4

NO multiplied the first for 2

14x + 4y=-2
3x - 4y=19
17x=17, x=1

7+2y=-1,y=-4

Answer 5

Hello,

Multiply the first one by 2 giving us 14x + 4y = -2
Now add it to the second one and we have.

7x = 17 so x = 1

Put this back into the first on giving us 7*(1) + 2y = -1 then 2y = -8 and y = -4.

Hope This Helps!

Answer 6

You upload the equations jointly to eliminate between the variables, then clean up for the the rest variable. so as to eliminate on the variables, their coefficients must be opposites. as an occasion: 2x -3y -x -2x 3y x on occasion you need to multiply one or the two between the equations so as to get between the variables to be eradicated once you upload them. 5) 5x + 5y= -5 3x - y = -7 you could eliminate y from the equations in case you multiply the 2nd by using 5. (3x - y = -7)(5)----------------->15x -5y= -35 Now upload the 1st equation and your new 2nd equation, and clean up for x. 5x + 5y = -5 15x - 5y = -35 ------------------- 20x = -40 x=-2 Now you have x, so positioned that into one in all your unique equations and clean up for y. 3x - y = -7 3(-2)-y = -7 -6 - y = -7 -y = -a million y = a million So your answer is: (-2, a million) you could eliminate the two x or y, whichever is greater convienient.

Answer 7

7x+2y=-1
3x-4y=19

its easier if you multiply the top equation by 2

14x+4y=-2
3x-4y=19
11x=17
x=17/11

and plug 17/11 in for x, to find y