求 w/l 之值
1+根號2and1-根號2
_________________欲速則不達
求?解阿...因該部是常數解吧
_________________dodo61411@yahoo.com.tw我只是苗小的幼草~~!
:w/l=(l-2w)/ww²=l²-2wlw²-l²+2wl=0同除l²(w/l)²-1+2(w/l)=0(w/l)²+2(l/w)-1=0令(w/l)=xx²+2x-1=0x=-1+根號2 and -1-根號2(負不合)所以w/l=(根號2)-1
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原來是利用些小技巧(換元法)
_________________The art of doing mathematics consists in finding that special case which contains all the germs of generality
(w+l)²-2l²=0〔w+(1+√2)L〕〔W+(1-√2)L〕=0當1.w+(1+√2)L=0 W=-(1+√2)L 負值 所以不合理2.W+(1-√2)L=0 W=-(1-√2)L W=(√2-1)L所以L/W=1/(√2-1)
kc81731 寫道::w/l=(l-2w)/ww²=l²-2wlw²-l²+2wl=0同除l²(w/l)²-1+2(w/l)=0(w/l)²+2(l/w)-1=0令(w/l)=xx²+2x-1=0x=-1+根號2 and -1-根號2(負不合)所以w/l=(根號2)-1
把W設1,L/W=L不影響答案W/L=(L-2W)/W1/L=L-21=(L*L)-2L0=L*L-2L-1L=[2±√(4+4) ]/2(代乘法公式)L=1+√2(化簡)L/W=1+√2如果有看不懂的或我寫錯ˋ打錯的請寄jason_kung1992@yahoo.com.tw