1.(x+1/4)的平方-(x-1/4)(x-1/4)=1/4说明 [(x+1/4)+(x-1/4)]*[(x+1/4)-(x-1/4)]=1/4即 2x*1/2=1/4 所以2x=1/2 x=1/42.(x+1)(x-1)-(x+20)的平方=7说明 x^2-1-(x^2+40x+400)=7即 -40x=408 得x=10.2