长方形的周长是36。已知长比宽的二倍少三,这个长方形的长和宽各是多少?
(1)设宽为x,则长为2x+3cm,根据题意得:2(x+2x+3)=36;(2)设送给老师的单价为x元,则送给同学的是每本(x-8)元,
根据题意得:10x+50(x-8)=800.
绛旓細瑙:鍋囪闀挎柟褰鐨勯暱涓篈锛屽涓築銆2A+2B=36锛孉=2B-3銆2X(2B-3)+2B=36锛4B-6+2B=36锛6B=42锛孊=7锛孉=2B-3锛孉=11锛岃繖涓暱鏂瑰舰鐨勯暱鏄11锛屽鏄7銆
绛旓細锛1锛夎瀹戒负x锛屽垯闀夸负2x+3cm锛屾牴鎹鎰忓緱锛2锛坸+2x+3锛=36锛涳紙2锛夎閫佺粰鑰佸笀鐨勫崟浠蜂负x鍏冿紝鍒欓佺粰鍚屽鐨勬槸姣忔湰锛坸-8锛夊厓锛屾牴鎹鎰忓緱锛10x+50锛坸-8锛=800锛
绛旓細璁闀挎柟褰㈢殑瀹涓簒cm锛屽垯闀夸负锛氾紙2x+3锛塩m锛屾牴鎹鎰忓彲寰楋細 2锛坸+2x+3锛=36锛 瑙e緱锛歺=5锛 鍒欓暱涓猴細2脳5+3=13锛坈m锛夛紝 鏁呴暱鏂瑰舰鐨勯潰绉槸锛5脳13=65锛坈m 2 锛夛紟 绛旓細闀挎柟褰㈢殑闈㈢Н鏄65cm 2 锛
绛旓細绛:杩欎釜闀挎柟褰鐨勯潰绉槸77骞虫柟鍘樼背銆
绛旓細闀夸笌瀹界殑闀垮害鍜岋細36梅2锛18锛坈m锛夐暱涓庡鐨勯暱搴﹀樊锛4cm 闀匡細锛18+4锛壝2锛11锛坈m锛夊锛11锛4锛7锛坈m锛夐潰绉細11脳7锛77锛坈m锛夌瓟锛氳繖涓闀挎柟褰㈢殑闈㈢Н鏄77骞虫柟鍘樼背銆
绛旓細[(36梅2)-2]梅2 =[18-2]梅2 =8(鍘樼背)(8+2)x8=80(骞虫柟鍘樼背)绛:闀挎柟褰㈢殑闈㈢Н鏄80骞虫柟鍘樼背銆
绛旓細鍛ㄩ暱鏄涓や釜闀垮姞涓婁袱涓 涓や釜闀挎瘮涓や釜瀹藉叡澶氫簡4+4=8鍘樼背 36-8=28鍘樼背 28梅4=7鍘樼背锛屽涓7鍘樼背锛岄暱涓7+4=11鍘樼背銆傞潰绉负7脳11=77骞虫柟鍘樼背銆傜瓟锛闀挎柟褰㈢殑闈㈢Н涓77骞虫柟鍘樼背銆
绛旓細瑙:璁闀挎柟褰㈢殑瀹戒负x鍘樼背锛屽垯闀夸负x+6鍘樼背銆傛牴鎹鎰忔湁: 2(x+x+6)=36锛屽嵆2x+6=18 2x=12锛寈=6鍘樼背锛寈+6=12鍘樼背 璇ラ暱鏂瑰舰鐨勯潰绉疉=6脳12=72 骞虫柟鍘樼背
绛旓細璁惧鏄痻 锛14+2x锛墄2=36 瑙=2锛岄暱2+14=16
绛旓細1銆侀暱鏂瑰舰鍛ㄩ暱涓36鍘樼背锛屽懆闀跨瓑浜3鍊嶇殑闀垮拰瀹界殑鍜岋紝鍙緱闀垮拰瀹界殑鍜屼负18鍘樼背銆2銆闀挎柟褰㈢殑闈㈢Н绛変簬闀涔樺锛岃闀縜鍘樼背锛屽b鍘樼背锛岄偅涔堟湁a+b=18鍘樼背銆3銆佸師鏉ョ殑闀挎柟褰㈤潰绉负ab骞虫柟鍘樼背锛屽鍔犲悗鐨勯潰绉负(a+4)(b+4)=ab+4a+4b+16=ab+4(a+b)+16=ab+88骞虫柟鍘樼背锛屾墍浠ラ暱鏂瑰舰鐨勯潰绉瘮鍘熸潵鐨...