x1-x2的绝对值=根号下（x1+x2）的平方-4x1x2的公式怎么用，运用于那种数学题 根据韦达定理怎么推得：|x1-x2|=根号[(x1+x2)^...
\u4e3a\u4ec0\u4e48x1-x2\u7684\u7edd\u5bf9\u503c=\u6839\u53f7\u4e0b\uff08x1+x2\uff09\u7684\u5e73\u65b9-4x1x2,\u5177\u4f53\u600e\u4e48\u63a8\u51fa\u6765\u7684\u554a\uff0c\u8c22\u8c22\u5566\u56e0\u4e3a
\uff08x1+x2\uff09\u7684\u5e73\u65b9-4x1x2=(x1\u7684\u5e73\u65b9+x2\u7684\u5e73\u65b9+2x1x2)-4x1x2=x1\u7684\u5e73\u65b9+x2\u7684\u5e73\u65b9-2x1x2=(x1-x2)\u7684\u5e73\u65b9
\u8fd9\u4e0d\u662f\u6839\u636e\u97e6\u8fbe\u5b9a\u7406\u63a8\u7684\uff0c\u662f\u4e58\u6cd5\u516c\u5f0f\uff1a
(x1+x2)²=x1²+x2²+2x1x2
(x1-x2)²=x1²+x2²-2x1x2
\u4e24\u5f0f\u76f8\u51cf\u5f97\uff1a
(x1+x2)²-(x1-x2)²=4x1x2
\u6240\u4ee5\uff0c(x1-x2)²=(x1+x2)²-4x1x2
\u5373\uff1a|x1-x2|²=(x1+x2)²-4x1x2
\u6240\u4ee5\uff0c|x1-x2|=\u6839\u53f7[(x1+x2)^2-4x1x2]
\u795d\u4f60\u5f00\u5fc3\uff01\u5e0c\u671b\u80fd\u5e2e\u5230\u4f60\uff0c\u5982\u679c\u4e0d\u61c2\uff0c\u8bf7\u8ffd\u95ee\uff0c\u795d\u5b66\u4e60\u8fdb\u6b65\uff01O(\u2229_\u2229)O
首先可以用于求|x1-x2|
其次 在解析几何中 常应用
尤其是在直线和曲线相交求交点间线段长度时。
|X1-X2|=根号下(X1-X2)的平方=X1的平方-2X1X2+X2的平方=根号下（X1+X2）-4X1X2
绛旓細(1)璁剧洿绾挎枩鐜囦负k,鐩寸嚎涓庡弻鏇茬嚎浜や簬宸﹀彸涓ゆ敮,璇存槑k鐨勭粷瀵瑰<娓愯繎绾跨殑鏂滅巼 鑼冨洿涓(-涓夊垎涔嬫牴鍙蜂笁锛屼笁鍒嗕箣鏍瑰彿涓)锛2锛夌洿绾挎柟绋嬩负y=x+2 涓庡弻鏇茬嚎鑱旂珛寰楀埌2x^2+12x+15=0 x1-x2鐨勭粷瀵瑰=鏍瑰彿涓[(x1+x2)^2-4x1*x2]=鏍瑰彿6 AB=(x1-x2鐨勭粷瀵瑰)*鏍瑰彿2=2鍊嶆牴鍙3 鍛ㄩ暱=AB+AF2+BF2=...
绛旓細鎬ユ眰!!涓轰粈涔x1-x2鐨勭粷瀵瑰=鏍瑰彿涓(x1+x2)鐨勫钩鏂-4x1x2涓昏鏄牴鍙蜂笅鐨勯儴鍒嗗叿浣撴槸鎬庝箞鏉ョ殑,璋㈣阿鍟!1涓洖绛 #鐑# 鑱屽満涓婂彈濮斿眻瑕佷笉瑕佷负鑷繁瑙ｉ噴?feng123h0 2013-12-21 路 TA鑾峰緱瓒呰繃6125涓禐 鐭ラ亾澶ф湁鍙负绛斾富 鍥炵瓟閲:2849 閲囩撼鐜:100% 甯姪鐨勪汉:2159涓 鎴戜篃鍘荤瓟棰樿闂釜浜洪〉 鍏虫敞 ...
绛旓細鑰锛坸1-x2)²=(x1+x2)²锛4x1*x2 ( 娉ㄦ剰涓嬮潰杩欎竴姝ワ紝鏄妸x1-x2褰撲綔鏈煡鏁板埄鐢ㄧ洿鎺ュ紑骞虫柟娉曟潵姹傜殑,)鏍规嵁骞虫柟鏍圭殑瀹氫箟鍙緱 x1-x2=卤鈭歔(x1+x2)²锛4 x1*x2]=卤鈭歔(-3/2)²锛4锛堬紞1/2锛塢=卤鈭17/2 2,鑷充簬涓轰粈涔堚滈殢渚垮姞缁濆鍊鈥濄傞鍏堬紝浣犵殑寮忓瓙鏄...
绛旓細|x1-x2|=鈭(x1-x2)^2=鈭(x1^2-2x1x2+x2^2)=鈭(x1^2+2x1x2+x2^2-4x1x2)=鈭歔(x1+x2)^2-4x1x2]=鈭歔(-b/a)^2-4c/a]=鈭歔(b^2-4ac)/a^2]=鈭氣柍/|a|
绛旓細|x1-x2| =鈭(x1-x2)²=鈭歔(x1+x2)²-4x1x2]
绛旓細闊﹁揪鍏紡鐨勮繍鐢x1-x2鐨勭粷瀵瑰涓鍏冧簩娆℃柟绋嬩腑浠ｈ〃涓や釜鏍瑰湪鏁拌酱涓婄殑璺濈锛屽洜涓锛圶1+X2锛塣2-4X1*X2=X1^2+X2^2-2X1*X2=(x1-x2)^ 2鎵浠ュ氨鐢▅(x1-x2)|=(锛圶1+X2锛塣2-4X1*X2)^1/ 2 鍐嶇粨鍚堥煢杈惧畾鐞嗘潵姹傚嚭x1-x2鐨勭粷瀵瑰 ...
绛旓細|x1-x2|=鈭锛坸1+x2锛塣2-4x1x2 鐒跺悗澶ф鏄埄鐢ㄤ簩鍏冧竴娆℃柟绋嬫牴涓庣郴鏁扮殑鍏崇郴锛屽彲浠ュ緱 x1+x2=D x1x2=F 甯﹀叆鍗冲彲銆
绛旓細x1➖x2鐨勭粷瀵瑰鏄粈涔 =鈭(x1-x2)²=鈭歔(x1+x2)²-4x1x2]=鈭(b²-4ac) /|a|
绛旓細|x1-x2|=鏍瑰彿涓嬶紙X1锛峏2锛夌殑骞虫柟 =鏍瑰彿涓媅锛圶1+X2锛²-4x1x2]=[鏍瑰彿涓(b²-4ac)]/|a|
绛旓細瑙:鈭祒1锛寈2婊¤冻缁濆鍊硷紙X1-X2锛=鈭5,鈭(x1-x2)^2=5,鈭祒1.x2骞冲潎鏁版槸x=(x1+x2)/2.鈭存柟宸=[(x1-x)^2+(x2-x)^2]/2 =[(x1-x2)^2/4+(x2-x1)^2/4]/2 =[2(x1-x2)^2/4]/2 =(x1-x2)^2/4 =5/4
