(1)x+2y=13 (2)y=2x-7

1个回答

  • (1)x+2y-2*(y+2z)+4*(z+2x)=9x=45 x=5 5+2y=13 y=4 z+10=13 z=3

    (2)5x+3*(2x-7)+2z+(3x-4z)/2=12.5x-21=4 12.5x=25 x=2 y=4-7=-3 6-4z=4 z=0.5

    (3)b=1-a-c 9a+3*(1-a-c)+c=3+6a-2c=9 6a-2c=6 ①3a-c=3

    25a+5*(1-a-c)+c=5+20a-4c=5 20a-4c=0 ②a=5c

    由①,②得:a=15/14 c=3/14 b=1-a-c=-4/14

    (4)2x+3y-2*(x-y)=5y=5 y=1 x-1=1 x=2

    2-m=0 m=2