Question

You're supposed to do subsitution.
-4x + y = 6
-5x - y = 21

Answer 1

Any ideas?

Answer 2

isolate 'y' from 1st equation by adding 4x on both sides, what you get ?

Answer 3

Are you still there?

Answer 4

Yeah.

Answer 5

so did you add 4x to both sides ?

Answer 6

Do you know what the "substitution principle" is?

Answer 7

Aren't you supposed to substitute y first?

Answer 8

for that you need to find y=.. from 1st equation

Answer 9

@hartnn i got x + y = 6 ... Im not very bright.

Answer 10

@aye4angela you can substitute either for "x" or "y" but you first should understand what the "substitution principle" is.

Answer 11

-4x+y=6
Adiing 4x on both sides will give you
-4x+4x+y=6+4x
y=4x+6
got this ?

Answer 12

Ohhhhhhhh. :3

Answer 13

And then you substitute that y= into the next equation?

Answer 14

yes.

Answer 15

replace 'y' by '4x+6' in 2nd equation

Answer 16

so that you get a equation in only 'x'
which can be solved easily :)

Answer 17

did you substitute that y= into the next equation ??
what you got ?

Answer 18

You can "replace 'y' by '4x+6' in 2nd equation" because the substitution principle allows you to replace an expression by another expression that has the same value.

Answer 19

On the 2nd equation i got 20x = 51. :/ i don't think im right.

Answer 20

-5x-y =21
-5x-(4x+6)=21
how did you get 20x ?
did you multiply 4 and 5 ??

Answer 21

Yeah. @hartnn

Answer 22

-5x-(4x+6)=21
now you have to open the brackets,
-5x -4x -6 =21
yes!
did you get this ?

Answer 23

How did it turn to minus 6? That's what i always get mixed up on.