Solve the system of equations by adding or subtracting x 2y

Solve the system of equations by adding or subtracting. {-x - 2y = 15 3x + 2y = -9 The solution of the system is

Solution

Solution : Adding the given equations, to get

-x+3x-2y+2y = 15+(-9)

2x+0 = 15-9

2x = 6

x = 6/2

Thus x= 3.

Substituting x=3 in the first equation, to get

-3+2y=15

2y = 15 + 3

2y = 18

y = 18/2

=9

Therefore solution of the given system is (3, 9).