一个直角梯形的下底比上底长2厘米，高比上底短1厘米，面积是8cm的平方，求梯形上底是多少？用方程解 一个直角梯形的下底比上底长2㎝，高比上底短1㎝，面积是8平方...

\u4e00\u4e2a\u76f4\u89d2\u68af\u5f62\u5f97\u4e0b\u5e95\u6bd4\u4e0a\u5e95\u957f2cm\uff0c\u9ad8\u6bd4\u4e0a\u5e95\u77ed1cm\uff0c\u9762\u79ef\u662f8 \u5e73\u65b9\u79bb\u7c73\uff0c\u753b\u51fa\u8fd9\u4e2a\u68af\u5f62

\u8bbe\u4e0a\u5e95\u4e3ax\uff0c\u5219\u4e0b\u5e95\u4e3ax+2\uff0c\u9ad8\u4e3ax-1
\u68af\u5f62\u9762\u79ef\uff1a1/2*\uff08x+x+2\uff09*\uff08x-1\uff09=8
x²-1=8\u2192x=\u00b13\uff0cx=-3\u6392\u9664\uff0cx=3
\u6240\u4ee5\u68af\u5f62\u7684\u4e0a\u5e95\u4e3a3\uff0c\u4e0b\u5e95\u4e3a5\uff0c\u9ad8\u4e3a2

\u8bbe\u4e0a\u5e95\u4e3aX\uff0c\u5219\u4e0b\u5e95\u4e3aX+2\uff0c\u9ad8\u4e3aX-1\u3002
[X+\uff08X+2\uff09]\u00d7\uff08X-1\uff09\u00f72=8
\uff082X+2\uff09\uff09\u00d7\uff08X-1\uff09=16
2X^2=18
X=3\u5398\u7c73
\u5219\u4e0b\u5e95\u4e3a:3+2=5\u5398\u7c73\uff0c

设上底X厘米
[X+（X+2）]×（X-1）÷2=8
（2X+2）（X-1）=16
2（X+1）（X-1）=16
（X+1）（X-1）=8
X=3

设上底为x，（x-1）（x+x+2）÷2=64

涓涓洿瑙掓褰㈢殑涓嬪簳姣斾笂搴曢暱2鍘绫,楂樻瘮涓婂簳鐭1鍘樼背,闈㈢Н鏄8cm鐨勫钩鏂...
绛旓細2锛圶+1锛夛紙X-1锛=16 锛圶+1锛夛紙X-1锛=8 X=3

涓涓洿瑙掓褰㈢殑涓嬪簳姣斾笂搴澶2cm,,楂樻瘮涓婂簳灏1cm,闈㈢Н绛変簬8cm^2,鐢诲嚭杩...
绛旓細绗竴涓紝璁涓婂簳涓篨锛涓嬪簳涓篨+2锛岄珮涓篨-1锛岄潰绉=锛堜笂搴+涓嬪簳锛*楂橀櫎浠2锛屾墍浠ヨВ鏂圭▼寰椾笂搴曟槸3cm涓嬪簳鏄3+2=5cm锛岄珮鏄3-1=2cm锛岀敾鍥惧氨绠鍗曚簡

涓涓褰,瀹鐨勪笅搴曟瘮涓婂簳闀2cm,瀹冪殑楂樹负3cm,璁惧畠鐨勪笂搴曢暱涓簒cm,瀹冪殑闈...
绛旓細锛1锛墆=3x+3锛寈鏄嚜鍙橀噺锛寉鏄洜鍙橀噺锛涳紙2锛夊綋x鐢5cm鍙樺埌7cm鏃讹紝y鐢18鍒24锛涳紙3锛夊鍥撅細锛4锛夋瘡澧炲姞1cm鏃讹紝y澧炲姞3cm锛岀悊鐢3锛坸+1锛+3-[3x+3]=3锛5锛夐潰绉兘绛変簬9cm2=9锛寈=2锛涓婂簳鏄2锛涢潰绉笉鑳界瓑浜2cm23=2x=-13锛屽簳杈逛笉鑳芥槸璐熸暟锛...

涓姊舰鐨勪笅搴曟瘮涓婂簳澶2cm,楂樻槸5cm,闈㈢Н鏄40c銕,姹備笂搴曘傗栬В鏂圭▼鈥?
绛旓細璁涓婂簳鏄痻锛屽洜涓涓嬪簳姣斾笂搴曞2cm锛屾墍浠ヤ笅搴曞氨鏄痻+2锛屾牴鎹姊舰鐨勯潰绉叕寮忓緱锛坸+2+x锛壝5梅2=40锛岃В涔嬪緱x=7锛屽嵆涓婂簳涓7cm銆

涓涓褰㈢殑涓嬪簳姣斾笂搴澶2cm,楂樻槸5cm,闈㈢Н鏄40cm,姹備笂搴曞垪鍑烘柟绋
绛旓細姊舰鐨勪笂搴曢暱搴涓7cm銆傝В锛氳姊舰鐨勪笂搴曚负xcm銆傞偅涔堟牴鎹鎰忓彲鍒楁柟绋嬩负锛(x+x+2)x5梅2=40 (2x+2)=40x2梅5 2x+2=16 x=7 鍗虫褰㈢殑涓婂簳涓7cm銆

姹傝鍒楃畝鍗曟柟绋嬨涓涓褰笅搴曟瘮涓婂簳澶2鍘绫,楂5鍘樼背,闈㈢Н40鍘樼背骞虫柟...
绛旓細鍥炵瓟锛氳繖涓緢绠鍗曘傞鍏堟垜浠涓婂簳涓:x 璁涓嬪簳涓:y 閭ｄ箞涓嬪簳鎴戜滑鏍规嵁棰樼洰鍙煡鏄:x+2=y 鐢姊舰闈㈢Н鍏紡: (x+y) *5/2=40 瑙ｅ嚭璇ユ柟绋嬪嵆鍙傛渶鍚庢垜浠彲鐭ヤ笂搴曚负:x=7 涓嬪簳:y=9

濡傚浘鏄涓涓洿瑙掓褰,涓婂簳銆涓嬪簳鍜岄珮鐨勯暱搴﹀垎鍒槸2鍘绫炽4鍘樼背鍜4鍘 ...
绛旓細脳4梅2=6脳4梅2=12锛堝钩鏂瑰帢绫筹級12梅锛1+2+3锛=2锛堝钩鏂瑰帢绫筹級2脳2=4锛堝钩鏂瑰帢绫筹級2脳3=6锛堝钩鏂瑰帢绫筹級鎵鍒嗗壊鐨勫浘褰㈢殑闈㈢Н鍒嗗埆鏄2骞虫柟鍘樼背锛4骞虫柟鍘樼背锛6骞虫柟鍘樼背锛涘皢鐩磋姊舰鐨鐩磋杈瑰钩鍒4鍒嗭紝涓嬪簳骞冲垎4浠斤紝涓婂簳鍜屼笅搴曠殑椤剁偣鍒嗗埆杩炴帴鐩磋姊舰鐩磋杈圭殑涓偣锛屾妸姊舰鍒嗘垚浜1锛2锛3鐨3涓浘褰紟

涓涓暟瀛﹂棶棰:涓涓洿瑙掓褰,涓嬪簳鏄涓婂簳鐨3鍊嶃傚鏋滃皢涓婂簳寤堕暱10鍘樼背灏...
绛旓細鎬濊矾锛氫笅搴曟槸涓婂簳鐨3鍊嶏紝鍒欒鏄涓嬪簳姣斾笂搴曢暱2鍊 灏嗕笂搴曞欢闀10鍘樼背寰楀埌姝ｆ柟褰紝鍒欒鏄庯細1銆佷笅搴曟瘮涓婂簳闀10鍘樼背锛2銆姊舰楂樹笌涓嬪簳涓鏍烽暱 鍏蜂綋鍋氭硶锛氫笂搴曪細10/锛3锛1锛夛紳5鍘樼背 涓嬪簳锛3*5锛15鍘樼背 鍘熸褰㈤潰绉細锛5锛15锛*15/2锛150骞虫柟鍘樼背 ...

涓涓洿瑙掓褰㈢殑涓嬪簳姣斾笂搴曢暱3cm
绛旓細濡傛灉涓婂簳澧炲姞3鍘樼背,灏卞彉鎴愪簡姝ｆ柟褰,璇存槑杩欎釜姊舰鐨勪笂搴曟瘮涓嬪簳灏3鍘樼背,涓嬪簳鍜岄珮涓鏍烽暱 涓婂簳鏄15-3=12鍘樼背 闈㈢Н鏄紙15+12锛墄15梅2=202.5骞虫柟鍘樼背

涓涓洿瑙掓褰,涓婂簳涓涓嬪簳鐨勯暱搴︽瘮鏄3:5,鑻ユ妸涓婂簳澧炲姞6鍘樼背,涓嬪簳澧炲姞2...
绛旓細璁涓婂簳涓3x.涓嬪簳涓5x锛屽洜涓轰笂搴曞姞6锛屼笅搴曞姞2浼氭垚涓涓鏂瑰舰锛屾墍浠3x+6=5x+2 x=2.鎵浠3x+6=12.鎵浠ヤ笂搴曚负6.涓嬪簳涓10.鎵浠=锛6+10锛壝12梅2=96