Question

3x+5y=15 2x-3y=-4 igualcion no la logro entender

Answer 1

[1] 3x + 5y = 15
[2] 2x - 3y = -4

Despejando x en [1] y [2]
3x + 5y = 15
x = 15/3 - 5y/3      [3]

2x - 3y = -4
x = -4/2 + 3y/2     [4]

[3] = [4]
(15-5y)/3 = (-4 + 3y)/2
2(15 - 5y) = 3(-4 + 3y)
30 - 10y = -12 + 9y
-10y - 9y = -12 - 30
-19y = -42
y = 42/19

Reemplazando y en [4]
x = -2 + (3/2)(42/19)
x = -2 + 126/38
x = (-76 + 126)/38
x = 50/38

Comprobando x, y en [2]
2x - 3y = -4
2(50/38) - 3(42/19) = -4
100/38 - 126/19 = -4
(100 - 252)/38 = -4
-152/38 = -4
    -4 = -4