Question

Por favor galera , me ajudem a fazer estas 4 primeiras perguntas obg *-

Answer 1

Ola Haad

a)

x - y = 3
x + y = 9

2x = 12
x = 6

6 - y = 3
y = 6 - 3 = 3

b)

2x - 2y = 12
x + 2y = 11

3x = 23
x = 23/3

2y = 33/3 - 23/3 = 10/3
y = 5/3

c)

x + y = 7
x + 2y = 11

2y - y = 11 - 7
y = 4

x + 4 = 7
x = 7 - 4 = 3

d)

-3x - 2y = 8
x - 5y = 3

3x - 15y = 9

-17y = 17
y = -1

x = 3 + 5y = 3 - 5 = -2

Answer 2

A) $\left \{ {{x-y=3} \atop {x+y=9}} \right.$
2x=12
x=$\frac{12}{6}$
x=6
6+y=9
y=$\frac{9}{6}$ (simplifica por 3)
y=$\frac{3}{2}$

B) $\left \{ {{2x-2y=12} \atop {x+2y=11}} \right.$
x=23
23+2y=11
2y=11-23
y= $\frac{12}{2}$
y= -6

C) $\left \{ {{x+y=7(-1)} \atop {x+2y=11}} \right.$ ~ $\left \{ {{-x-y=-7} \atop {x+2y=11}} \right.$
y=3
x+3=7
x=7-3
x=4