Question

若X的平方减x减1等于零,求x的5次方分之x的4次方加2x加1的值

Answer 1

x² -x -1 =0 即 x² = x+1

分母 x^5 = x²*x*x*x= ( x+1)*x*x*x = (x²+x)*x*x

= (2x+1)*x*x = (2x²+x )*x

= (2(x+1)+x)*x = (3x+2)*x .(1)

= (3x²+2x)

= 3(x+1) +2x

= 5x +3

分子

x^4 +2x +1 = 由.(1) = (3x+2) +2x+1 = 5x+3

分子/分母 = 1