Question

how much is 2x+3y-10 if
a) 2x+3y-4=25
b)4x+6y=18?

Answer 1

Hmm. This is easy (very) when you think a little about it.

Answer 2

\[2x + 3y - 10 \implies 2x + 3y - 4 - 6\]Do you agree with the above?

Answer 3

@sarmandi ?

Answer 4

ah i dont really understand :(

Answer 5

Never mind, just tell me if you agree with that one.

Answer 6

how did u get -6 ?

Answer 7

Here's how:\[2x + 3y \color{red}{- 10}\]\[\implies 2x + 3y \color{red}{-4 - 6}\]

Answer 8

aha okey i got it :D ty :D

Answer 9

And did you get the second?

Answer 10

no i will try do it :D

Answer 11

Good job! :)

Answer 12

ty man ;)

Answer 13

Right, let's do it!
What do you get when you multiply 2 to (2x + 3y - 10)?

Answer 14

4x+6x-10 or`?

Answer 15

6y*

Answer 16

Actually, 4x + 6y - 20... not 10 :)

Answer 17

OK, let's leave the 4x + 6y - 20 for a while. Returning back to the equation, what do you get by subtracting 20 from both sides in the following?\[4x + 6y = 18\]

Answer 18

18-19=-1 ??

Answer 19

I repeat: subtract 20 FROM BOTH SIDES in the equation — \(4x + 6y = 18\)

Answer 20

i dont understand what u mean :/

Answer 21

\[4x +6y =18 \implies 4x + 6y - 20 = 18 - 20 \]Do you agree?

Answer 22

yes

Answer 23

Okay, simplifying the right-hand-side,\[4x + 6y - 20 = -2\]Now we know that \(2(2x + 3y - 10) = 4x + 6y - 20\) right?

Answer 24

yes

Answer 25

So,\[2(2x + 3y - 10) = 2(-1)\]Agree?

Answer 26

how u got -1?

Answer 27

Well, isn't \(-2 = 2(-1)\)?

Answer 28

answer in book is -1

Answer 29

Yeah, the book is right ;)

Answer 30

We have \(2(2x + 3y -10) = 2(-1)\).
Cancel 2 from both sides!

Answer 31

ty its right

Answer 32

=)

Answer 33

how much is 2x+3y-10 if
b)4x+6y=18

I think I would factor 2 from the left side in (b) to get
2(2x+3y)= 18 (hoping it will match the question. It looks like it does!)
divide both sides of the equation by 2
2x+3y= 9

that looks helpful. replace 2x+3y in the original question with 9:
2x+3y-10 becomes 9-10 or simply -1