解:X(X+19)=8100 X^2+19X-8100=0 (X+100)(X-81)=0 X1=-100,X2=81
X(X+19)=8100 X^2+19X-8100=0 (X+100)(X-81)=0 X1=-100,X2=81
(x+100)(x-81)=0x=-100或81
x=81,-100