Question

Solve.

{3x+y=42x+y=5

Use the linear combination method.

A.) (-3,12)
B.) (-3,13)
C.) (0,4)
D.) (-1,7)

Answer 1

3x + y = 4
2x + y = 5....multiply by -1
--------------
3x + y = 4
-2x - y = -5 (result of multiplying by -1)
-------------add
x = -1

3x + y = 4
3(-1) + y = 4
-3 + y = 4
y = 4 + 3
y = 7

solution is (-1,7)

Answer 2

(D)(-1,7)

Explanation:

We want to solve for x and y in the simultaneous equation

3x+y=4

2x+y=5

Subtract Equation 2 from Equation 1

x=-1

Substitute x=-1 into any of the equations to solve for x.

3x+y=4

3(-1)+y=4

-3+y=4

y=4+3=7

Therefore: (x,y)=(-1,7)