Question

resolva pelo processo de substituição

a) x+y=17
x=13

b) 2x+y=23
y=5

c) 2x+y=21
x=12

d) x+y=26
y=x-4​

Answer 1

a)

$Condi\c c\~ao:x=13\\x+y=17\\13+y=17y=17-13\\ \boxed{y=4}\\ \\\\S=\{4\}$

b)

$Condi\c c\~ao:y=5\\2x+y=23\\2x+5=23\\2x=23-5\\2x=18\\x=\frac{18}{2}\\ \boxed{x=9^}\\ \\\\S=\{9\}$

c)

$Condi\c c\~ao:x=12\\2x+y=21\\2\cdot12+y=21\\24+y=21\\y=21-24\\ \boxed{y=-3}\\ \\\\S=\{-3\}$

d)

$Condi\c c\~ao: y=x-4\\x+y=26\\x+x-4=26\\2x=26+4\\2x=30\\x=\frac{30}{2}\\ \boxed{x=15}\\ \\ \\S=\{15\}$

Bons estudos!