Question

me ajude....
a) {x+2y=4
2x-y=0
b) {x+2y=2
x-y=13
c) {4x-y=-1
5x-y=1​

Answer 1

Olá,

a)

$x + 2y = 4 \\ 2x - y = 0 \: ( \times 2) \\ \\ 4x - 2y = 0 \\ x + 2y = 4 \\ 5x = 4 \\ x = 4 \div 5 \\ x = \frac{4}{5} = 0.8 \\ \\ x + 2y = 4 \\ 0.8 + 2y = 4 \\ 2y = 4 - 0.8 \\ 2x = 3.2 \\ x = 3.2 \div 2 \\ x = 1.6$

b)

$x + 2y = 2 \\ x - y = 13 \: ( \times 2) \\ \\ 2x - 2y = 26 \\ x + 2y = 2 \\ 3x = 28 \\ x = \frac{28}{3} \\ \\ x - y = 13 \\ \frac{28}{3} - y = 13 \\ \\ - y = 13 - \frac{28}{3} \\ \frac{ - 3y}{3} = \frac{39}{3} - \frac{28}{3} \\ \\ - 3y = 39 - 28 \\ - 3y = 11 \\ y = \frac{11}{ - 3} \\ y = - \frac{11}{3}$

c)

$4x - y = - 1 \\ 5x - y = 1( \times - 1) \\ \\ - 5x + y = - 1 \\ 4x - y = - 1 \\ - x = - 2 \\ x = 2 \\ \\ 4x - y = - 1 \\ 4(2) - y = - 1 \\ 8 - y = - 1 \\ - y = - 1 - 8 \\ - y = - 9 \\ y = 9$

Espero ter ajudado :-) Boa sorte.