4x 3y 2z=15,则x y z=?
已知x 2y 3z=10, 4x 3y 2z=15,则x y z=? 已知x+2y+3z=10, 4x+3y+2z=15,则x+y+z=?快快快，很急
已知x+2y+3z=10, 4x+3y+2z=15,则x+y+z=?快快快，很急 3x+y-z=5 2x-y-4z=-5 5x-5z=0 x=z qiu2x+y because4x+2y=10 so2x+y=5 x+y+z=5
(1).(2)=5x+5y+5z=25 5(x+y+z)=25 x+y+z=5
x+2y+3z=10,4x+3y+2z=15,把两式加起来，得：5X+5Y+Z=25，所以，X+Y+Z=5
x + 2y + 3z = 10 ------ (1) 4x + 3y + 2z =15 ------ (2) (1) + (2) ---> 5 (x + y + z) = 25 x + y + z = 5 这道题很活,如果能想到就很简单,想不到就很难
x+2y+3z=10得X=10-2Y-3Z代入第二个式子得以Y＝5－2Z,则X+Y+Z=5
两式相加得5X+5Y+5Z=25，
得X+Y+Z=5
x + 2y + 3z = 10 ------ (1) 4x + 3y + 2z =15 ------ (2) (1) + (2) ---> 5 (x + y + z) = 25 x + y + z = 5
答：设:x/3=y/4=z/5=k 则:x=3k,y=4k,z=5k 则:(x+y+z)/(2x-3y+5z)=12k/19k=12/19详情>>
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