Question

已知x+1的4次方

已知x+1/x=3,求x4+1/x4的值
1/x是：x分之1 x4是x的4次方 1/x4是：x的4次方分之1

Answer 1

x+1/x=3
(x+1/x)^2=3^2
x^2+1/x^2+2=9
x^2+1/x^2=7
(x^2+1/x^2)^2=7^2
x^4+1/x^4+2=49
x^4+1/x^4=47
(^为乘方,x^2为x的平方)