Question

resolva os sistemas de equações.
a) x + y = 9
x - y = 7

b) 3x - y = 4
x + y = 2

c) -2x + y = 7
x + 3y = 0

Answer 1

a) x + y = 9
 x - y = 7x= 9-y
x-y=7 > 9-y-y=7 > 9-2y=7 > 2y=2> y=1
x= 9-y > x= 9-2 > x=7 b) 3x - y = 4
 x + y = 2x=2-y
3x-4=4 > 3.2-y-4=4 > 6-y-4 =4 > -y=-6+4+4> -y=2 .(-1)> y=2
x=2-y > x=2-2 x=0c) -2x + y = 7
 x + 3y = 0x=-3y
-2.(-3y)+y=7 > 6y+y=7 > 7y=7 > y=1
x=-3.1 > x=-3