估一估．yf÷4≈ 4y0÷f≈ 1yf÷1≈ 35f÷1≈ f3÷f≈ 310÷5≈ 410÷y≈ 323÷4

1/4+3/4\u00f71/2=

1/4+3/4\u00f71/2
=1/4+3/4x2
=1/4+6/4
=7/4
=1.75

1.\u6839\u53f7f\u7684\u51e0\u4f55\u610f\u4e49\u662f\uff1a
\u70b9\uff08a,1/a\uff09\u4e0e\u70b9\uff08b,-b\uff09\u7684\u8ddd\u79bb
\u82e5\u8981\u6c42\u4ed6\u7684\u7684\u6700\u5c0f\u503c
\u4e5f\u5373
\u9898\u76ee\u53ef\u6539\u4e3a\uff1a
\u6c42y=1/x\u4e0ey=-x\u4e4b\u95f4\u7684\u6700\u8fd1\u7684\u8ddd\u79bb\u70b9\u5750\u6807
\u663e\u7136
\u4e24\u4e2a\u56fe\u50cf\u5173\u4e8ey=x\u8f74\u5bf9\u79f0\uff0c\u4e14\u8ddd\u79bb\u6700\u8fd1\u53d1\u751f\u5728
\uff081\uff0c1\uff09\uff0c\uff080\uff0c0\uff09\u65f6
\u4ee5\u53ca
\uff08-1\uff0c-1\uff09\uff0c\uff080\uff0c0\uff09\u65f6
\u5373
\u539f\u5f0f\u4e2dx=1,y=0\u65f6
f\u53d6\u5230\u6700\u5c0f\u503c=2
2 .
1\uff0f\uff082+x\uff09+1\uff0f\uff082+y\uff09=1\uff0f3
3\uff0f\uff082+x\uff09+3\uff0f\uff082+y\uff09=1
\u901a\u5206\uff0c\u53bb\u5206\u6bcd3y+6+3x+6=xy+2x+2y+4
xy=x+y+8>=2\u6839\u53f7xy+8 \u6362\u5143\u4ee4\u6839\u53f7xy=t
\u5f97t^2-2t-8>=0
(t-4)(t+2)>=0
t>=4
xy>=16
3.
\u7531\u5df2\u77e5\uff0c|OA|=|OB|=|OC|=1 \uff0c\u4e14 OA*OB=cos120= -1/2 \uff0c
\u56e0\u6b64\u7531\u5df2\u77e5\u5f97 OC^2=x^2+y^2+2xy*OA*OB \uff0c
\u5373 x^2+y^2-xy=1 \uff0c
\u6240\u4ee5 (x+y)^2-3xy=1 \uff0c
\u7531\u4e8e xy<=(x+y)^2/4 \uff0c
\u5219 (x+y)^2-1=3xy<=3/4*(x+y)^2 \uff0c
\u89e3\u5f97 x+y<=2 \uff0c
\u5373\u5f53 x=y=1 \u65f6\uff0cx+y \u6700\u5927\u503c\u4e3a 2 \u3002

估一估． 70÷4≈2w； 47w÷0≈九； 170÷九≈ww； w59÷九≈九w； 0w÷9≈9； w九w÷5≈7w； 41w÷7≈九w； w2w÷4≈0w．

扩展阅读：估一估431 73 ... 4x+3y 100怎么解 ... s3 40% ... 3.141至100图片 ... 二十四点计算器 ... x方 4x+3 0详解 ... 男人不能试 一试全剧终 ... 免疫组化ki67 十40% ... x+y+2z 400详细解 ...