Question

considerando que y = 7x -3, determine o valor da incógnita x nas equações :

a) 2x + 5y = 59

b) 3 x - y = 21

c) 5 x - 3y = - 2

d) 0, 3x - 0, 2 y = 1,7​

Answer 1

Resposta:

$a)~~2x+5(7x-3)=59\\ \\ 2x+35x-15=59\\ \\ 37x=59+15\\ \\ 37x=74\\ \\ x=\frac{74}{35} \\ \\ x=2$

$b)~~3x-(7x-3)=21\\ \\ 3x-7x+3=21\\ \\ -4x=21-3\\ \\ -4x=18\\ \\ x=-\frac{18}{4} =-\frac{9}{2} =-4,5$

$c)~~5x-3(7x-3)=-2\\ \\ 5x-21x+9=-2\\ \\ -16x=-2-9\\ \\ -16x=-11~~.(-1)\\ \\ 16x=11\\ \\ x=\frac{16}{11}$

$d)~~0,3x-0,2(7x-3)=1,7\\ \\ 0,3x-1,4x-0,6=1,7\\ \\ 0,3x-1,4x=1,7+0,6\\ \\ -1,1x=2,3\\ \\ x=-\frac{2,3}{1,1} \\ \\ x=2,0909090...$