请帮我计算下下面的数学题,请写出步骤,a2+4a-1=0求a2+1/a-2=

Question

请帮我计算下下面的数学题,请写出步骤,
a2+4a-1=0 求a2+1/a-2=

Answer 1

a2+4a-1=0
a+4-1/a=0
a-1/a=-4
(a-1/a)^2=16
a^2+1/a^2-2=16
a^2+1/a^2=18