Question

resolva os sistemas

Answer 1

$a)\\ \\ x=5y~....~eq~I\\ 7x-20y=45~...eq~II\\ \\ Substitua~(x=5y)~na~equacao~II:\\ \\ 7(5y)-20y=45\\ \\ 35y-20y=45\\ \\ 15y=45\\ \\ y=\frac{45}{15} \\ \\ y=3\\ \\ substitua~(y=3)~na~equacao~I\\ \\ x=5y\\ \\ x=5.3\\ \\ x=15~~~~~~~~~~S=(x=15;~~y=3)$

$b)\\ \\ 5x-y=4~....~eq~I\\ x-y=8~...~eq~II\\ \\ Na~equacao~II:\\ \\ x-y=8\\ \\ x=8+y\\ \\ Substitua~(x=8+y)~na~equacao~I:\\ \\ 5x-y=4\\ \\ 5(8+y)-y=4\\ \\ 40+5y-y=4\\ \\ 5y-y=4-40\\ \\ 4y=-36\\ \\ y=-\frac{36}{4} \\ \\ y=-9\\ \\ Substitua~(y=-9)~na~equacao~II:\\ \\ x-y=8\\ \\ x-(-9)=8\\ \\ x+9=8\\ \\ x=8-9\\ \\ x=-1~~~~~~~~~~~~~S=(x=-1;~~y=-9)$