contestada

Select all correct answers. 12. The solution to the system of equations x y = 1 and x - y = - 7 is (- 3, 4) This solution is NOT a solution to which of the following equations? x y - 2(x - y) = 1 - 2(- 7) B 3(x y) x - y = 3(1) - 7 C x y 5(x - y) = 5(1) - 7 D - 4(x y) x - y = 1 - 4(- 7) E x y - x y = 1 7

Respuesta :

Answer:(-3, 4).

Step-by-step explanation:

Let's check each option to see if the given solution, (-3, 4), satisfies the equation:

A.

2

(

)

=

1

2

(

7

)

xy−2(x−y)=1−2(−7)

(

3

)

(

4

)

2

(

(

3

)

4

)

=

1

2

(

7

)

(−3)(4)−2((−3)−4)=1−2(−7)

(

12

)

2

(

7

)

=

1

14

(−12)−2(−7)=1−14

12

+

14

=

1

14

−12+14=1−14

2

=

13

2=−13 (False)

B.

3

(

)

=

3(xy)=x−y

3

(

(

3

)

(

4

)

)

=

(

3

)

4

3((−3)(4))=(−3)−4

3

(

12

)

=

3

4

3(−12)=−3−4

36

=

7

−36=−7 (False)

C.

5

(

)

=

5

(

1

)

7

xy−5(x−y)=5(1)−7

(

3

)

(

4

)

5

(

(

3

)

4

)

=

5

7

(−3)(4)−5((−3)−4)=5−7

12

5

(

7

)

=

2

−12−5(−7)=−2

12

+

35

=

2

−12+35=−2

23

=

2

23=−2 (False)

D.

4

(

)

=

−4(xy)=x−y

4

(

(

3

)

(

4

)

)

=

(

3

)

4

−4((−3)(4))=(−3)−4

4

(

12

)

=

3

4

−4(−12)=−3−4

48

=

7

48=−7 (False)

E.

=

1

7

xy−xy=1−7

(

3

)

(

4

)

(

3

)

(

4

)

=

1

7

(−3)(4)−(−3)(4)=1−7

12

+

12

=

6

−12+12=−6

0

=

6

0=−6 (False)