Question

Solve using elimination.

7x + 4y = -3
-7x + 5y = 12

(
,
)

Questions

Answer 1

(x, y ) → (- 1, 1 )

given the 2 equations

7x + 4y = - 3 → (1)

- 7x + 5y = 12 → (2)

add (1) and (2) term by term to eliminate x

(7x - 7x ) + (4y + 5y ) = (- 3 + 12 )

9y = 9 ( divide both sides by 9 )

y = 1

substitute y = 1 into either (1) or (2) and solve for x

(1) : 7x + 4 = - 3 ( subtract 4 from both sides )

7x = - 7 ( divide both sides by 7 )

x = - 1

solution is (x, y ) → (- 1, 1 )

Answer 2

Just adding the 2 equations eliminates the terms in x (7x + -7x = 0) giving:-

0 + 9y = 9

y = 1

Plug this into the first equation:-

7x + 4(1) = -3

7x = -7

x = -1

Answer x = -1 and y = 1.