Question

x等于2分之根号5减1则x的4次方加x的2次方加5x减1~

Answer 1

x=(√5-1)/2

2x=√5-1

2x+1=√5

(2x+1)^2=5

4x^2+4x+1=5

x^2+x-1=0

x^2=1-x

x^4=(1-x)^2=1-2x+x^2=1-2x+1-x=2-3x

x^4+x^2+5x-1

=(2-3x)+(1-x)+5x-1

=2+x

=(√5+3)/2