Question

已知：x-x分之1=-2 x²-3x+1=0 求x²+x²分之1

Answer 1

(1)

x-1/x=-2

(x-1/x)²=(-2)²

x²+1/x²-2=4

x²+1/x²=6

(2)

x²-3x+1=0

x-3+1/x=0 (除以x得）

x+1/x=3

(x+1/x)²=3²

x²+1/x²+2=9

x²+1/x²=7