Question

solve the system by substitution 2x+y=-11 3x-4y=11 choices A.(3,5) B.(-5,-3) C.(-3,-5) D.(5,3)

Answer 1

C. try substituting the values in option C

Answer 2

okay what about solve the system using elimination 2x+6y=-12 5x-5y=10 choices A.(2,1) B.(0,-2) C.(-2,0) D.(1,2)

Answer 3

For elimination methosd,
2x+6y=-12 ---> (1)
5x-5y=10 --->(2)

Let's make both eqn (1) and eqn (2) have 10x in them.
to do so, multiply.

So for (1), multiply by 5.
it'll become 10x+30y=-60 ---> (3)

for (2), multiply by 2.
it'll become 10x-10y=20 --->(4)

Answer 4

Then to eliminate 10x, take (3)-(4)
so,
10x+30y-(10x-10y) = -60 - 20
40y=-80
y=-2 :)

then sub y=-2 into (1)
2x+6(-2)=-12
2x=0
x=0 :)

Answer 5

do u understand?

Answer 6

okay so you jus make both equations have a common number in them

Answer 7

yes that's right

Answer 8

okay thanks!!

Answer 9

np

Answer 10

i was watching , i would like to comment on the first problem "solve using substitution.

Answer 11

what about it?

Answer 12

you do not just substitute given answers to see if it satisfies the equation you do it like this

2x+y=-11
3x-4y=11

first solve for a variable , y would be easiest because it is by itself in equation 1

y= -11 -2x subtracted 2x from both sides

and then substitute that in for y in the 2nd equation like so:

3x- 4( -11 -2x) =11

and then solve

Answer 13

once you get an answer for x plug that back in to get y and do not forget to do your checks

Answer 14

do you mulitply -4 and -11 and -4 and -2x?

Answer 15

yes

Answer 16

okay so you get 3x-44-8x=11 do you combine like terms (the 3x and -8x)

Answer 17

-4 times -2x is positive

Answer 18

3x and 8x pay careful attention to your signs

Answer 19

so now i have 11x+44=11 subtract 44 from both sides and get 11x=-33

Answer 20

yes

Answer 21

now what

Answer 22

divide both sides by 11 to isolate x

Answer 23

x=-3

Answer 24

so the anwser is C

Answer 25

yes take that and plug it in on of the equations and solve for y

Answer 26

alright thanks for your help

Answer 27

yes good job!!!!
remember to plug your x and y values in both equations as a check