Question

已知x+x的-1次方=a，求x方+x的-2方和x的4次方+x的-4次方的值

不会打数学符号，大家对付着看

Answer 1

（x+x^-1）^2=a^2
x^-2+x^2+2=a^2
so,x^2+x^-2=a^2-2
x^4+x^-4=(a^2-2)^2-2

Answer 2

x+1/x=a则x^2+1/x^2=a^2-2 x^4+1/x^4=a^4-4a^2+2

Answer 3

x+1/x=a
(x+1/x)²=x²+2+1/x²=a²
x²+1/x²=a²-2
x四次方+x的-4次方=(x²+1/x²)²-2=a的四次方-4a²-6

Answer 4

x+1/x=a => (x+1/x)²=x²+2+1/x²=a² => x²+1/x²=a²-2

x²+1/x²=a²-2 => (x²+1/x²)² = x^4+1/x^4+2 = (a²-2)² => x^4+1/x^4 =(a²-2)²-2=a^4-4a²+2

^4表示4次方