某自来水公司水费计算办法如下：若每户每月用水不超过5m3，则每立方米收费1.5元；若每户每月用水超过5m3
\u67d0\u81ea\u6765\u6c34\u516c\u53f8\u6c34\u8d39\u8ba1\u7b97\u529e\u6cd5\u5982\u4e0b\uff1a\u82e5\u6bcf\u6237\u6bcf\u6708\u7528\u6c34\u4e0d\u8d85\u8fc75\u7acb\u65b9\u7c73\uff0c\u5219\u6bcf\u7acb\u65b9\u7c73\u6536\u8d391.5\u5143\uff0c\u82e5\u6bcf\u6237\u6bcf\u6708\u7528\u6c34\u8d85\u8fc7\u8bbe\u5f20\u5bb61\u6708\u4efd\u7528\u6c34\u91cf\u4e3a2x\u7acb\u65b9\u7c73\uff0c\u674e\u5bb6\u4e3a3x\u7acb\u65b9\u7c73\uff1a5\u00d71.5=7.5\uff08\u5143\uff09\uff0c17.5-7.5=10\uff08\u5143\uff09\uff0c27.5-7.5=20\uff08\u5143\uff09\uff0c\u53ef\u5f97102x?5\uff1d203x?5\uff0c 2\uff082x-5\uff09=3x-5\uff0c 4x-10=3x-5\uff0c x=5\uff0c10\u00f7\uff082\u00d75-5\uff09=2\uff08\u5143\uff09\uff1b\u7b54\uff1a\u8d85\u51fa5\u7acb\u65b9\u7c73\u7684\u90e8\u5206\u6bcf\u7acb\u65b9\u7c73\u6536\u8d392\u5143\uff0e\u6545\u7b54\u6848\u4e3a\uff1a2\uff0e
\u8bbe\u8d85\u51fa5m3\u7684\u90e8\u5206\u6bcf\u7acb\u65b9\u7c73\u6536\u8d39x\u5143\uff0c\u4f9d\u9898\u610f\u5f97\uff0c17.5?1.5\u00d75x+5=23\uff0827.5?1.5\u00d75x+5\uff09\u89e3\u5f97x=2\uff0c\u7ecf\u68c0\u9a8cx=2\u4e3a\u65b9\u7a0b\u7684\u89e3\uff0e\u5373\u8d85\u51fa5m3\u7684\u90e8\u5206\u6bcf\u7acb\u65b9\u7c73\u6536\u8d392\u5143\uff0e\u6545\u9009B\uff0e
设超过5m3的部分每立方米收费x元．根据题意小王与小李家的用水量超过5立方米，
可得：5+
| 17.5?5×1.5 |
| x |
| 2 |
| 3 |
| 27.5?5×1.5 |
| x |
解得：x=2．
经检验，x=2是原方程的解，且符合题意．
∴超过5m3的部分每立方米收费2元．
绛旓細1.5脳5=7.5鍏.17.5-7.5=10鍏 27.5-7.5=20鍏 璁惧皬鍗庡瓒呭嚭5m³179;鍚庣殑鐢ㄦ按閲忎负xm³锛屽垯灏忚帀瀹惰秴鍑5m³鐨勭敤姘撮噺涓2x³鎵浠5+x=2(5+2x)/3锛岃В寰梮=5m³10梅5=2鍏.瓒呭嚭5m³鐨勯儴鍒嗘瘡绔嬫柟绫冲姞鏀2鍏.
绛旓細鐢ㄦ埛鐢ㄦ按瓒呰繃5绔嬫柟绫虫椂鏀惰垂澶氫簬7.5鍏冿紝鐜嬪姘磋垂17.5锛屽垯瓒呰繃浜5绔嬫柟绫炽傝鏉庡鐢ㄦ按涓篨锛屽垯鐜嬪鍗2X/3锛岃瓒呭嚭閮ㄥ垎姣忕珛鏂圭背鏀惰垂Y鍏冿紝鍒欏垪鍑烘柟绋嬬粍{7.5+锛圶-5锛*Y=27.5 7.5+锛2X/3-5锛*Y=17.5}銆傝В寰梄=15 Y=2 鍗崇瓟妗堜负2鍏冦傛湁甯姪璇风偣濂借瘎鎴栬呴噰绾 绁濅綘鏂扮殑涓瀛︽湡瀛︿範杩涙锛
绛旓細1銆佺敤鎴风敤姘磋秴杩5绔嬫柟绫虫椂鏀惰垂澶氫簬7.5鍏冿紝鐜嬪姘磋垂17.5锛屽垯瓒呰繃浜5绔嬫柟绫炽傝鏉庡鐢ㄦ按涓篨锛屽垯鐜嬪鍗2X/3锛岃瓒呭嚭閮ㄥ垎姣忕珛鏂圭背鏀惰垂Y鍏冿紝鍒欏垪鍑烘柟绋嬬粍{7.5+锛圶-5锛*Y=27.5 7.5+锛2X/3-5锛*Y=17.5}銆傝В寰梄=15 Y=2 鍗崇瓟妗堜负2鍏冦
绛旓細[(42.5-27.5)*3-42.5]/5+2=(45-42.5)/5+2=2.5鍏
绛旓細璁捐秴鍑洪儴鍒唜鍏冩瘡鍚紝鍒欐湁锛氬皬鍗庣敤姘撮噺=锛17.5-1.5脳5锛壝穢+5=5+10/x;灏忔潕瀹剁敤姘撮噺=(5+10/x)脳(3/2)=15/2+15/x;璐圭敤=27.5=15/2+15/x;15/x=20;x=15/20;x=0.75;瓒呭嚭閮ㄥ垎姣忓惃0,75鍏冿紱濡傛灉鏈鏈変粈涔堜笉鏄庣櫧鍙互杩介棶锛屽鏋滄弧鎰忚寰楅噰绾 濡傛灉鏈夊叾浠栭棶棰樿閲囩撼鏈鍚庡彟鍙戠偣鍑诲悜...
绛旓細瑙ｏ細璁捐秴杩5m3鐨勯儴鍒嗘瘡绔嬫柟绫虫敹璐箈鍏冿紟鏍规嵁棰樻剰锛屽緱锛5+(17.5-5脳1.5)x=2/3脳锛5+27.5-5脳1.5)/x 瑙ｄ箣锛屽緱x=2锛庣粡妫楠岋紝x=2鏄師鏂圭▼鐨勮В锛屼笖绗﹀悎棰樻剰锛庘埓瓒呰繃5m3鐨勯儴鍒嗘瘡绔嬫柟绫虫敹璐2鍏冿紟
绛旓細鏂圭▼寮忔槸 灏忔潕瀹剁敤姘撮噺x,瓒呰繃5m³鐨勯儴鍒嗘瘡绔嬫柟绫虫敹璐箉鍏 1.5*5+(2x/3-5)y=17.5 1.5*5+(x-5)y=27.5 x=15 y=2 瓒呰繃5m³鐨勯儴鍒嗘瘡绔嬫柟绫虫敹璐2鍏
绛旓細璁炬潕瀹剁敤姘撮噺涓篨 锛屽垯寮犲鐢ㄦ按2/3 X 锛岃秴杩囬儴鍒嗘按閲忎环鏍间负Y锛屽彲鍒濡備笅鏂圭▼锛1.5脳5+锛圶-5锛塝=27.5 1.5脳5+锛2/3 X -5锛塝=17.5 锛岃仈绔嬶紝鍙В锛寈y=30锛屽啀鎶婃鍊煎甫鍏ユ柟绋1鎴栬呮柟绋2鍒欏彲瑙=2
绛旓細璁捐秴杩5m³鐨勬瘡绔嬫柟绫虫敹璐箈鍏 澧ㄥⅷ瀹跺綋鏈姘磋垂鏄24.5鍏冿紝鍒欏ⅷ澧ㄥ瓒呭嚭鐨勬按閲忎负 锛24.5-2.5脳5锛/x =12/x 灏忔捣瀹跺綋鏈堟按璐规槸40.5鍏 鍒欏皬娴峰瓒呭嚭鐨勬按閲忎负 锛40.5-2.5脳5锛/x =28/x 澧ㄥⅷ瀹剁敤姘撮噺鏄皬娴峰鐢ㄦ按閲忕殑涓夊垎涔嬩簩 12/x+5=2/3脳锛5+28/x锛 涓よ竟鍚屾椂涔樹互3x 36...
绛旓細1.鏌愯嚜鏉ユ按鍘傚叕鍙告按璐硅绠楀姙娉曞涓嬶細姣忔埛姣忔湀鐢ㄦ按涓嶈秴杩5绔嬫柟绫崇殑锛屾瘡绔嬫柟绫虫敹璐0.85鍏冿紝瓒呭嚭閮ㄥ垎姣忕珛鏂圭背鏀跺彇杈冮珮鐨勫畾棰濊垂鐢紝宸茬煡7鏈堜唤寮犲鐢ㄦ按閲忎笌鏉庡鐢ㄦ按閲忕殑姣旀槸2锛3锛屽紶瀹跺綋鏈堟按璐14.6鍏冿紝鏉庡褰撴湀姘磋垂涓22.65鍏冦傛眰瓒呭嚭5绔嬫柟绫崇殑閮ㄥ垎姣忕珛鏂圭背鏀惰垂澶氬皯鍏冿紵瑙ｏ細鐢变簬0.85脳5=4.25<14.6<22....
