(a+b)(a-b)=a2-b2 (a+b)2=a2+2ab+b2 (a-b)2=a2-2ab+b2
9 e6 C% h. N; i' {(a+b)3=a3+3a2b+3ab2+b3 (a-b)3=a3-3a2b+3ab2-b35 j) S; N7 J: x" v3 s" f4 N6 p0 t
一元二次方程ax2+bx+c=0的解x₁,₂=(-b±√b2-4ac)/2a0 e c4 Q+ }7 K# M0 W7 A
*Simple Interest:利息Interest=本金Principal时间Time利率Rate。/ m- C! o1 r3 c4 t7 I' ~! M1 ]' `
*Compound Interest:A=P(1+R)n;A为本利和，P为本金,R为利率,n为期数。0 s: h9 {* `# i
*Discount=CostRate of Discount *Distance=SpeedTime; E0 u7 _4 q: U# A# y) k
*Pythagorean Theorem(勾股定理):直角三角形(right triangle)两直角边(legs)的平方和等于斜边 (hypotenuse)的平方。! q7 B. S: e) J& [" y
*多边形的内角和：(n-2)×180°，总对角线数为n(n-3)/2条，从每一个顶点引出的对角线数为(n-3)条；式中：n为多边形的边数$ b' s: _+ y( e4 ~! e v
*平面直角坐标系中，A(x1,y1)和B(x2,y2)是任意两点，C(x,y)是线段AB的中点，则& v9 X; M8 w$ G/ x+ g
x=(x1+x2)/2,,y=(y1+y2)/2,线段AB两端点间的距离= 0 ~! n4 d$ A4 A6 f( _6 H, J
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发表于 2012-8-15 12:55:17
