X，Y，Z是三个有理数，若X<Y，X+Y=0，且XYZ>0，判断X+Z的符号(要有过程)。 x，y，z是指三个有理数，若x>y,x+y=0,且xyz>0...
x\uff0cy\uff0cz\u662f\u4e09\u4e2a\u6709\u7406\u6570\uff0c\u82e5x<y\uff0cx+y=0\uff0c\u4e14xyz>0\uff0c\u8bd5\u5224\u65adx+z\u7684\u7b26\u53f7\u3002\u8d1f\u53f7
XY\u4e92\u4e3a\u76f8\u53cd\u6570\uff0c\u6240\u4ee5XY<0\uff0c
\u7531\u4e8exyz>0 \u63a8\u51faZ<0
\u56e0\u4e3aX0
X+Z<0
\u9898\u76ee\u51fa\u9519\u4e86\u5427\u2026\u2026\u4e0d\u662f\u5224\u65adx+y\u5427\u2026\u2026\uff0cx+y\u662f\u5df2\u77e5\u7684\u2026\u2026
x+y=o,x>y,\u8bf4\u660ex>0,y<0,\u4e14|x|=|y|
xyz>0.\u8bf4\u660ez<0
\u5982\u679c\u9898\u76ee\u662fy+z,\u80af\u5b9a\u662f\u5c0f\u4e8e0\u7684\u3002
\u5982\u679c\u662fx+z\uff0c\u4e0d\u77e5\u9053z\u7684\u7edd\u5bf9\u503c\uff0c\u4e0d\u80fd\u5224\u65ad\u5440\u3002
\u770b\u770b\u4f60\u7684\u9898\u76ee\u5427\uff0c\u662f\u4e0d\u662f\u4f60\u6253\u9519\u4e86\u5440
∵X<Y,X+Y=0
∴X=-Y<0
∴XYZ=-X²Z
又∵XYZ>0
∴Z<0
∴X+Z<0
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绛旓細鍥炵瓟锛氣埖X<Y,X+Y=0 鈭碭=-Y<0 鈭XYZ=-X²Z 鍙堚埖XYZ>0 鈭碯<0 鈭碭+Z<0
绛旓細x+y=0 x鍜寉鏄浉鍙嶆暟 x<y 鎵浠<0,y>0 鎵浠xy<0 xyz>0 鎵浠 x<0y>0,z<0 x<0,z<0,鎵浠+z<0 z<0<y銆傛墍浠-y<0 鎵浠(x+z)(z-y)>0
绛旓細x+y=0,x<y,璇存槑x<0, -x=y>0 xyz>0,璇存槑 z<0 鎵浠+z<0 璇佹槑:鍥犱负x+y=0,鍙堝洜涓簒灏忎簬y鎵浠涓巠浜掍负鐩稿弽鏁,涓攛灏忎簬0,y澶т簬0.鍥犱负xyz澶т簬0.鎵浠灏忎簬0.鎵浠+z鐨勭鍙蜂负璐熷彿
绛旓細锛1锛夌敱x+y=0鍙緱x=-y 鍙坸<y 鎵浠-y<y锛鍙煡y鏄鏁 鍥犳x鏄礋鏁 鍥犱负xyz>0锛屼笖x<0锛寉>0 鎵浠z<0 锛2锛夊洜涓簒鍜寊鍧囦负璐熸暟锛屾墍浠+z涔熸槸璐熸暟 鍥犱负x鏄礋鏁帮紝y鏄姝ｆ暟锛屾墍浠-y鏄礋鏁 涓よ礋鏁扮浉涔樺緱姝ｆ暟 鍥犳(x+z)(x-y)鏄鏁 ...
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