Question

15x+11y=-23,-2x+7y=20 by elimination methods​

Answer 1

Correct option is

B

(−3,2)

15x+11y=−23 ----- (1)

−2x+7y=20 ----- (2)

First use formula for cross multiplication method:

b

1

c

2

−b

2

c

1

x

=

c

1

a

2

−a

1

c

2

y

=

a

2

b

2

−a

2

b

1

−1

So, from equation (1) and (2) we can write the value of a, b and c.

11×20−7×(−23)

x

=

(−23)×(−2)−15×20

y

=

15×7−(−2)×11

−1

220+161

x

=

46−300

y

=

105+22

−1

381

x

=

−254

y

=

127

−1

381

x

=

127

−1

x=

127

−381

=−3

−254

y

=

127

−1

y=

127

254

y=2

The solution is (−3,2).

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Answer 2

Answer:

-3

Step-by-step explanation:

11y + 5x = -23...(1)

7y - 2x = 20

x = (7y-20/2) = -23 (2)

Sub (2) from (1)

22y + 105y -300= -46

127y =254

y = 2

x = -3