Beartou.com 应用: 求值 题3设x,x2为方程x2-4x+1=0的两个根, x1+x)= 4 xX1·X 2 x2+x2=(x1+x2)2-2x2-14 2 )2=(x1+x2)2-4x1 12 2
1 2 2 x x 4 x 1 x 2 = 1 14 12 题３ 则： x 1 + x 2 = + = 22 21 x x + − 2 1 2 ( x x ) ＝ − = 2 1 2 ( x x ) 2 1 2 ( x + x ) 1 2 − 4 x x ＝ 应用： 一、求值
Beartou.com 另外几种常见的求值 11x1+x 1.+ X Ix X xX cc小 x (x1+x2)2-2x 2.-1+ 2 12 X X1x 3.(x1+1)(x2+1)=x1x2+(x1+x2)+1 4. x2|=V(x1-x12)2=√(x1+x2)2-4x1x
另外几种常见的求值 + = 1 2 1 1 1. x x 1 2 1 2 x x x + x 3.(x1 +1)(x2 +1) = x1 x2 + (x1 + x2 ) +1 1 2 2 1 2. x x x x + 1 2 2 2 2 1 x x x + x = 1 2 1 2 2 1 2 ( ) 2 x x x + x − x x = 4. x1 − x2 = 2 1 2 (x − x ) 1 2 2 1 2 = (x + x ) − 4x x