Question

若k的二次方减k再减2等于-1,k为何值

Answer 1

k²-k-2=-1

k²-k=1

k²-k+1/4=1+1/4=5/4

(k-1/2)²=(±√5/2)²

k-1/2=±√5/2

k=1/2±√5/2

所以k=(1-√5)/2或k=(1+√5)/2