用铁丝做一个底面形状是正方形,面积为16平方厘米,高是3厘米的长方体框架,至少需要铁丝( )厘米
\u81f3\u5c11\u9700\u8981\uff08\uff09\u5398\u7c73\u957f\u7684\u94c1\u4e1d\uff0c\u624d\u80fd\u505a\u4e00\u4e2a\u5e95\u9762\u79ef\u662f16\u5e73\u65b9\u5398\u7c73\u7684\u6b63\u65b9\u5f62,\u9ad8\u662f3\u5398\u7c73\u7684\u957f\u65b9\u4f53\u6846\u67b6.\u5c0f\u5b66\u4e94\u5e74\u7ea7\u77e5\u8bc6.
\u7b2c\u4e8c\u5355\u5143\u7684\u957f\u65b9\u4f53\u8ba4\u8bc6.
\u6c42\u957f\u65b9\u4f53\u7684\u68f1\u957f.
16=4*4
4*8+3*4=44(\u5398\u7c73)
\u8bbe\u4ed6\u5e95\u9762\u7684\u957f\u4e3aX\uff0c\u5bbd\u4e3aY\u3002 XY=16
\u7531\u4e8e X+Y>= 2\u00d7\u6839\u53f7\u4e0bXY \u6240\u4ee5\u6709X+Y>=8 \u53c8\u56e0\u4e3a\u9ad8\u4e00\u5b9a\uff0c\u6240\u4ee5\u9700\u8981\u94c1\u4e1d\u7684\u957f\u6700\u5c11\u4e3a
2\u00d7\uff08X+Y\uff09\u00d72+3\u00d74=44
绛旓細璁撅細闀挎柟浣撶殑杈归暱鏄疿鍘樼背锛岄偅涔堥珮鏄1/2X鍘樼背 4*x*2+(1/2X)*4=120 8x+2x=120 10x=120 x=12 閭ｄ箞楂樻槸锛1/2*12=6锛堝帢绫筹級闀挎柟浣撶殑浣撶Н=12*12*6=864锛堢珛鏂瑰帢绫筹級=0.864锛堢珛鏂瑰垎绫筹級銆愬悓瀛︼紝鐪嬫噦鍚楋紵銆戙愭偍鐨勫ソ璇勬槸瀵规垜鐨勮偗瀹氾紝璋㈣阿~銆
绛旓細閾佷笣闀 =锛4+4+6锛壝4 =14脳4 =56绔嬫柟鍒嗙背 ~涓鍒绘案杩523涓轰綘瑙ｇ瓟锛岀浣犲涔犺繘姝~~甯屾湜鍙互鍙婃椂鈥滈変负婊℃剰绛旀鈥濓紝浣犵殑閲囩撼鏄垜鍓嶈繘鐨勫姩鍔泘~~
绛旓細(80-5X4X2)梅4=10鍘樼背 ~甯屾湜瀵逛綘鏈夊府鍔╋紝璇峰強鏃剁偣鍑汇愰噰绾充负婊℃剰鍥炵瓟銆戞寜閽畘~鎵嬫満鎻愰棶鐨勬湅鍙嬪湪瀹㈡埛绔彸涓婅璇勪环鐐广愭弧鎰忋戝嵆鍙瘇~浣犵殑閲囩撼鏄垜鍓嶈繘鐨勫姩鍔泘~
绛旓細40-3脳4脳2=16cm 16梅4=4cm 鎵浠ユ槸4cm
绛旓細闀挎柟浣撶殑楂樻槸锕100锛7脳8锕毭4锛11鍘樼背
绛旓細鎮ㄥソ锛氶渶瑕 4x(8+8+3)=4x19=76鍘樼背 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鍙﹀彂鎴栫偣鍑诲悜鎴戞眰鍔╋紝绛旈涓嶆槗锛岃璋呰В锛岃阿璋傜瀛︿範杩涙锛
绛旓細瑕閾佷笣锛(5+5+4)*4=56鍘樼背 瑕佺殑绾革細锛5*5+5*4+5*4锛*2=130骞虫柟鍘樼背
绛旓細搴旇鏄鏂浣撴鏋跺惂锛佹鏂逛綋涓鍏辨湁12鏉℃１锛屾墍浠ユ瘡鏉℃１鐨勯暱搴︽槸60梅12=5鍒嗙背 鎵浠ュ叾浣撶Н鏄5脳5脳5=125绔嬫柟鍒嗙背
绛旓細濡傛灉瑕鍋氫竴涓簳闈鍛ㄩ暱涓30鍘樼背鐨姝ｆ柟褰紝鎴戜滑闇瑕佺煡閬撴鏂瑰舰鐨勮竟闀裤傚洜涓烘鏂瑰舰鐨勫洓杈归兘鐩哥瓑锛屾墍浠ュ彲浠ュ皢搴曢潰鍛ㄩ暱闄や互4鏉ュ緱鍒版鏂瑰舰鐨勮竟闀裤傚叿浣撳湴锛屾鏂瑰舰鐨勮竟闀夸负 30 鍘樼背 / 4 = 7.5 鍘樼背銆備负浜嗗埗浣滆繖涓鏂瑰舰锛岄渶瑕佺敤鍒板洓鏉¤竟闀跨浉绛夌殑閾佷笣鍥存垚姝ｆ柟褰㈢殑鍥涘懆銆傚洜姝わ紝鎴戜滑闇瑕佽绠楃殑鏄繖鏉￠搧涓濈殑...
绛旓細176鍘樼背閾佷笣锛1104骞虫柟鍘樼背
