Solve the following system of equations by linear combination:

4x + 3y = 12
y = x – 10

(–4, 6)
(6, –4)
(–7, 3)
(3, –7)

Question

Solve the following system of equations by linear combination:

4x + 3y = 12
y = x – 10


       (–4, 6)
       (6, –4)
       (–7, 3)
       (3, –7)

anonymous · Answer

4x + 3y = 12 
y = x - 10 ---> -x + y = -10 --> x - y = 10

so we have :
4x + 3y = 12
x - y = 10 --->(-4)
------------
4x + 3y = 12
-4x + 4y = -40 (result of multiplying by -4)
-----------add
7y = - 28
y = -4
now sub -4 in for y in either of the equations
y = x - 10
-4 = x - 10
-4 + 10 = x
6 = x

check...
4x + 3y = 12
4(6) + 3(-4) = 12
24 - 12 = 12
12 = 12 (correct)

x = 6 and y = -4 or (6,-4)