Question

1/(D^2+2D+2)=1/2-1/2D,怎么算出来的啊!

Answer 1

1/2-1/2D

=(D-1)/2D

1/(D^2+2D+2)

=1/[(D+1)^2+1]=(D-1)/2D

(D+1)^2+1=2D/(D-1)

(D+1)^2=2D/(D-1)-1=(D+1)/(D-1)

(D+1)^2-(D+1)/(D-1)=0

(D+1)[(D+1)-1/(D-1)]=0

D+1=0或(D+1)-1/(D-1)=0

(D+1)-1/(D-1)=0

(D+1)=1/(D-1)

(D+1)(D-1)=1

D^2=2

D=√2,或d=-√2或D=-1