Question

Решите уравнение x+y=12,x=3y

Answer 1

Это система уравнений?

Answer 2

y=12: 4

Answer 3

y=3

Answer 4

x+3=12

Answer 5

x=12-3

Answer 6

x=9

Answer 7

Ответ:

(9; 3).

Объяснение:

$left { begin{array}{lcl} {{x+y=12,} \ {x=3y;}} end{array} right.Leftrightarrowleft { begin{array}{lcl} {{3y+y=12,} \ {x=3y;}} end{array} right.Leftrightarrowleft { begin{array}{lcl} {{4y=12,} \ {x=3y;}} end{array} right.Leftrightarrow$

$Leftrightarrowleft { begin{array}{lcl} {{y=12:4,} \ {x=3y;}} end{array} right.Leftrightarrowleft { begin{array}{lcl} {{y=3,} \ {x=9.}} end{array} right.$