Question

-2x+7y=-9
7x+14y=-7
is the answer (1,-1),(-1,-1),(1,1) or (-1,1)?

Answer 1

Multiply the first equation by 2 :

-2x + 7y = - 9 ( multiply 2 both sides)
It will become
-4x + 14y = -18

Now, subtract this equation from the second equation :

7x + 14y - (-4x + 14y) = -7 - (-18)

7x + 14y + 4x - 14y = -7 + 18

Solve it further by cancelling out 14y.

Answer 2

so would the set be (-1,1)?

Answer 3

7x + 4x = 11
11x = 11
x = 1
and

-2x + 7y = -9
-2(1) + 7y = -9
-2 + 7y = -9

7y = -9 + 2
7y = -7
y = -1

so, it will be (1,-1)

Answer 4

You can always verify your result. Like you said that will it be (-1,1) ? then verify it..

you have 2 equations with you:

-2x+7y=-9
7x+14y=-7

put x = -1 and y = 1

i) -2(-1) + 7(1) = -9 ; 2 + 7 = -9 ; 9 = -9

9 is not equal to -9.. as we already know.

So, (-1,1) will not be our answer.

Answer 5

thanks

Answer 6

You're welcome :)