Question

classifique e resolva os sistemas lineares 2x2.

a) 3x+y=10
2x-3y=-8

b) 2x+5y=20
4x+10y=40

Answer 1

$3x++y=10 y=10/3 2x-3y=8 2x-3* \frac{10}{3} =8$
$2x- \frac{30}{3}=8$
2x-10=8
2x=8+10
2x=18/2
x=9

2)  2x++5y=20
2x=20-5y
x=20-5y/2
x=10-5y

4x+10y=40
4(10-5y)++10y=40
40-20y+10y=40
40-10y=40
-10y=40-40
y=0

substituindo 
2x+5y=20
2x+5*0=20
2x=20
x=20/2
x=10