Question

Пользуясь этим алгоритмом, решите системы уравнений:
х + у = 45
х – у = 13

х + у = 49
- х + у = 17

4х – 9у = 3
х + 3у = 6

15х – 4у = 8
- 3х + у = 1

3х – у = 7
6. 2х + 3у = 1

ПАМАГИТИ​

Answer 1

$\left \{ {{x+y=45} \atop {x-y=13}} \right. \\2x=58\\x=29\\29+y=45\\y=16\\(29;16)$

$\left \{ {{x+y=49} \atop {-x+y=17}} \right. \\2y=66\\y=33\\x+66=49\\x=-17\\(-17;66)$

$\left \{ {{4x-9y=3} \atop {x+3y=6}} \right. \\\left \{ {{4x-9y=3} \atop {3x+9y=18}} \right.\\7x=21\\x=3\\3*3+9y=18\\9y=9\\y=1\\(3;1)$

$\left \{ {{15x-4y=8} \atop {-3x+y=1}} \right. \\\left \{ {{15x-4y=8} \atop {-15x+5y=5}} \right.\\y=13\\-3x+13=1\\-3x=-12\\x=4\\(4;13)$

$\left \{ {{3x-y=7} \atop {6,2x+3y=1}} \right.\\ \left \{ {{9x-3y=21} \atop {6,2x+3y=1}} \right.\\15,2x=22\\x=\frac{38}{55} \\\\3*\frac{38}{55} -y=7\\2\frac{4}{55} -y=7\\-y=4\frac{51}{55} \\y=-4\frac{51}{55}\\\\(\frac{38}{55};-4\frac{51}{55})$