求几道利润问题的解法，急急急！ 求解！一道初一数学题！急急急急急急急急急急急急急~~~~~
\u6025\u6025\u6025\uff01\uff01\uff01\uff01\u6c42\u51e0\u9053\u9ad8\u4e00\u6570\u5b66\u9898\u7684\u89e3\u6cd5\uff01\uff01\uff01\u7b2c\u4e00\u9898\uff1a\u5e94\u8be5\u662f\u6c42\u8bc1\uff1a\uff08cos\u03b1\uff09^2/\uff3bcot\uff08\u03b1/2\uff09\uff0dtan\uff08\u03b1/2\uff09\uff3d\uff1d\uff081/4\uff09sin2\u03b1 \u5427\uff01
\uff08cos\u03b1\uff09^2/\uff3bcot\uff08\u03b1/2\uff09\uff0dtan\uff08\u03b1/2\uff09\uff3d
\uff1d\uff08cos\u03b1\uff09^2/\uff3bcos\uff08\u03b1/2\uff09/sin\uff08\u03b1/2\uff09\uff0dsin\uff08\u03b1/2\uff09/cos\uff08\u03b1/2\uff09\uff3d
\uff1d\uff08cos\u03b1\uff09^2sin\uff08\u03b1/2\uff09cos\uff08\u03b1/2\uff09/\uff5b\uff3bcos\uff08\u03b1/2\uff09\uff3d^2\uff0d\uff3bsin\uff08\u03b1/2\uff09\uff3d^2\uff5d
\uff1d\uff081/2\uff09\uff08cos\u03b1\uff09^2sin\u03b1/cos\u03b1
\uff1d\uff081/2\uff09cos\u03b1sin\u03b1
\uff1d\uff081/4\uff09sin2\u03b1\u3002
\u7b2c\u4e8c\u9898\uff1a
\u2235\u5411\u91cfa\uff0b\u5411\u91cfb\uff0b\u5411\u91cfc\uff1d0\uff0c\u2234\uff5c\u5411\u91cfa\uff5c\u3001\uff5c\u5411\u91cfb\uff5c\u3001\uff5c\u5411\u91cfc\uff5c\u6784\u6210\u4e86\u4e00\u4e2a\u4e09\u89d2\u5f62\u3002
\u8bbe\u5411\u91cfa\u4e0e\u5411\u91cfb\u7684\u5939\u89d2\u4e3a\u03b8\uff0c\u5219\u7531\u4f59\u5f26\u5b9a\u7406\uff0c\u6709\uff1a
cos\u03b8\uff1d\uff08\uff5c\u5411\u91cfa\uff5c^2\uff0b\uff5c\u5411\u91cfb\uff5c^2\uff0d\uff5c\u5411\u91cfc\uff5c^2\uff09/\uff082\uff5c\u5411\u91cfa\uff5c\uff5c\u5411\u91cfb\uff5c\uff09
\uff1d\uff089\uff0b25\uff0d49\uff09/\uff082\u00d73\u00d75\uff09\uff1d\uff0d1/2\uff0c
\u2234\u03b8\uff1d120\u00b0\u3002
\u5373\uff1a\u5411\u91cfa\u4e0e\u5411\u91cfb\u7684\u5939\u89d2\u4e3a120\u00b0\u3002
\u7b2c\u4e09\u9898\uff1a
\u2235\u5411\u91cfAM\uff1d\uff081/3\uff09\u5411\u91cfAB\u3001\u5411\u91cfAN\uff1d\uff081/3\uff09\u5411\u91cfAC\uff0c\u2234AM/AB\uff1dAN/AC\uff1d1/3\uff0c
\u2234MN\u2225BC\uff0c\u2234\u25b3AMN\u223d\u25b3ABC\u3001\u25b3PNM\u223d\u25b3PBC\u3002
\u7531\u25b3AMN\u223d\u25b3ABC\uff0c\u5f97\uff1aMN/BC\uff1dAM/AB\uff1d1/3\u3002
\u7531\u25b3PNM\u223d\u25b3PBC\uff0c\u5f97\uff1aPM/PC\uff1dMN/BC\uff1d1/3\uff0c\u2234PM\uff1d\uff081/4\uff09CM\u3002
\u2234\u5411\u91cfMP\uff1d\uff081/4\uff09\u5411\u91cfMC\u3002
\u800c\u5411\u91cfMC\uff1d\u5411\u91cfAC\uff0d\u5411\u91cfAM\uff1d\u5411\u91cfb\uff0d\uff081/3\uff09\u5411\u91cfAB\uff1d\u5411\u91cfb\uff0d\uff081/3\uff09\u5411\u91cfa\uff0c
\u2234\u5411\u91cfMP\uff1d\uff081/4\uff09\u5411\u91cfb\uff0d\uff081/12\uff09\u5411\u91cfa\uff0c
\u2234\u5411\u91cfAP\uff1d\u5411\u91cfAM\uff0b\u5411\u91cfMP\uff1d\uff081/3\uff09\u5411\u91cfAB\uff0b\uff081/4\uff09\u5411\u91cfb\uff0d\uff081/12\uff09\u5411\u91cfa
\uff1d\uff081/3\uff09\u5411\u91cfa\uff0b\uff081/4\uff09\u5411\u91cfb\uff0d\uff081/12\uff09\u5411\u91cfa
\uff1d\uff081/4\uff09\u5411\u91cfa\uff0b\uff081/4\uff09\u5411\u91cfb\u3002
\u5373\uff1a\u5411\u91cfAP\uff1d\uff081/4\uff09\u5411\u91cfa\uff0b\uff081/4\uff09\u5411\u91cfb\u3002
\u7b2c\u56db\u9898\uff1a
\u5f53\u7ef3\u5b50\u4e0e\u5730\u9762\u6240\u6210\u7684\u89d2\u4e3a\u03b8\u65f6\uff0c\u62c9\u529bF\u5728\u6c34\u5e73\u65b9\u5411\u4e0a\u7684\u5206\u529b\u4e3aFcos\u03b8\u3002\u3002
\u663e\u7136\uff0c\u5f53cos\u03b8\uff1d1\u65f6\uff0cFcos\u03b8\u7684\u503c\u6700\u5927\uff0c\u5373\u6b64\u65f6\u6700\u7701\u529b\u3002
\u7531cos\u03b8\uff1d1\uff0c\u5f97\uff1a\u03b8\uff1d0\u00b0\u3002
\u5373\uff1a\u7ef3\u5b50\u4e0e\u5730\u9762\u5e73\u884c\uff08\u7ef3\u5b50\u4e0e\u5730\u9762\u6240\u6210\u7684\u89d2\u4e3a0\u00b0\uff09\u65f6\uff0c\u6240\u7528\u7684\u62c9\u529bF\u6700\u5c0f\u3002
\u89e3\uff1a\uff081\uff09\u8bbe\u8fdb\u4ef7\u4e3a\u6bcf\u888ba\u5143\uff0c
\u5219\u5269\u4f59\u7684\u7535\u868a\u9999\u6bcf\u76d8\u83b7\u5229\u4e3a[a\uff081+40%\uff09\u00d770%-a]=0.98a-a=-0.02a\uff1c0\uff0c
\u7b54\uff1a\u5269\u4f59\u7684\u7535\u868a\u9999\u4ee5\u62537\u6298\u7684\u4f18\u60e0\u4ef7\u5356\u51fa\u4e8f\u635f\uff0e
\uff082\uff09\u8bbe\u5171\u4e70x\u888b\uff0c
\u636e\u9898\u610f\u5217\u65b9\u7a0b\u5f97\uff1a[a\uff081+40%\uff09-a]\u00d790%x+[a\uff081+40%\uff0970%-a]\u00d710%x-300=\uff0840%ax-300\uff09\u00d7\uff081-15%\uff09
\u89e3\u5f97\uff1aax=2500
\u7b54\uff1a\u4e70\u8fdb\u8fd9\u6279\u7535\u868a\u9999\u7528\u4e862500\u5143\uff0e
\u70b9\u8bc4\uff1a\u672c\u9898\u8003\u67e5\u4e00\u5143\u4e00\u6b21\u65b9\u7a0b\u7684\u5e94\u7528\uff0c\u5173\u952e\u5728\u4e8e\u627e\u51fa\u9898\u76ee\u4e2d\u7684\u7b49\u91cf\u5173\u7cfb\uff0c\u6839\u636e\u7b49\u91cf\u5173\u7cfb\u5217\u51fa\u65b9\u7a0b\u89e3\u7b54\uff0e
降低后的成本为：0.75X/（1+25%）=3/5X（元）。
成本降低了：2/3X-3/5X=X/15（元）。
或售价x，成本y，成本降低到z
0.8x=1.2y
0.75x=1.25z
得 9y=10z
成本降低了1／10
(2)96*20=1920
2040-1920=120
120/24=5
原售价100元，现售价85元，打85折
(3)30%*60%+｛30%-（1-0.8）｝*（100%-60%）
=18%+4%
=22%
答：实际利润率是22%。
(4)设成本价X
1.4*X*0.8-X=270
X=2250元
(5)解：设第二次降价后的是原定价格的y%
40% * [1*(1+38%)]+2 * y% * （1-40%）-1=0.302
0.552+ (y/50) *0.6-1=0.302
(3y/250)-1=0.302-0.552
(3y/250)=-0.25
12y-1000=-250
12y=-250+1000
12y=750
y=750/12
y=62.5
62.5/100=62.5%
55648
我只会方程，再说我也没时间回答
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绛旓細锛70000-20000锛壝25%+锛30000-20000锛壝7.5%=12500+750=13250锛堝厓锛堿鏌愬叡鑾峰彇13250鍏冦
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