Question

Решите систему уравнений
Зх+2у=8
4х–у=7

Answer 1

3х+2у=8
4х-у=7-введем замену у=4х-7
3х+2(4х-7)-8=0
3х+8х-14-8=0
11х-22=0
11х=22
Х=2
Подставляем
У=4х2-7
у=8-7
у=1
Ответ:х=2; у=1

Answer 2

$ttdisplaystyle left { {{3x+2y=8} atop {4x-y=7}} right. Longrightarrow left { {{3x+2y=8} atop {y=4x-7}} right. \\\3x+2(4x-7)=8\3x+8x-14=8\11x-14=8\11x=8+14\11x=22\x=22:11\x=2\\\y=4x-7\y=4*2-7\y=8-7\y=1$

Ответ: (2; 1)

Answer 3

Ответ:

(2; 1)

Объяснение:

$left { begin{array}{lcl} {{3x+2y=8,} \ {4x-y=7|*2;}} end{array} right. Leftrightarrow left { begin{array}{lcl} {{3x+2y=8,} \ {8x-2y=14;}} end{array} right.Leftrightarrow left { begin{array}{lcl} {11x{=22,} \ {4x-y=7;}} end{array} right. Leftrightarrow left { begin{array}{lcl} {{x=2,} \ {y=1.}} end{array} right.$