x+2y=10 (1)
2x-y=5 (2)
(1)+(2)×2
5x=20
x=4
y=2x-5=3
代入另两个
4a+3b=1 (3)
4b+3a=6 (4)
(3)+(4)
7a+7b=7
a+b=1
4a+4b=4 (5)
(5)-(3)
b=3
a=1-b=-2
x+2y=10 (1)
2x-y=5 (2)
(1)+(2)×2
5x=20
x=4
y=2x-5=3
代入另两个
4a+3b=1 (3)
4b+3a=6 (4)
(3)+(4)
7a+7b=7
a+b=1
4a+4b=4 (5)
(5)-(3)
b=3
a=1-b=-2