Question

For the following system, if you isolated x in the second equation to use the Substitution Method, what expression would you substitute into the first equation?

3x + y = 8
-x - 2y = -10

-2y + 10

2y + 10

2y - 10

-2y - 10

Answer 1

they want you to solve -x - 2y = -10 for x

Answer 2

what do I plug in for it?

Answer 3

nothing, you're just isolating x in that equation

Answer 4

example

if you had x+y = 10

isolating x would give you

x+y = 10

x+y-y = 10-y

x+0y = 10-y

x = 10-y

Answer 5

so 2y-10?

Answer 6

-x - 2y = -10

-x - 2y+2y = -10+2y .. Add 2y to both sides.

-x + 0y = -10 + 2y

-x = -10 + 2y

what's next?

Answer 7

divide -1
10-2y

Answer 8

good

x = 10 - 2y

x = 10 + (-2y)

x = -2y + 10

Answer 9

okay thank you!

Answer 10

np