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解?$：m2-8m=20$?
?$m2-8m+16=36$?
?$(m-4)2=36$?
?$m-4=±6$?
?$m_1=10，m_2=-2$?
解?$：x2+10x=2$?
?$x2+10x+25=27$?
?$(x+5)2=27$?
?$x+5=±3\sqrt{3}$?
?$x_1=-5+3\sqrt{3}，x_2=-5-3\sqrt{3}$?
解?$：y2+2\sqrt{2}y=-1$?
?$y2+2\sqrt{2}y+2=1$?
?$(y+\sqrt{2})2=1$?
?$y+\sqrt{2}=±1$?
?$y_1=-\sqrt{2}+1，y_2=-\sqrt{2}-1$?
解?$：x2-\frac {5}{2}x=-\frac {1}{2}$?
?$x2-\frac {5}{2}x+\frac {25}{16}=\frac {17}{16}$?
?$(x-\frac {5}{4})2=\frac {17}{16}$?
?$x-\frac {5}{4}=±\frac {\sqrt{17}}{4}$?
?$x_1=\frac {5+\sqrt{17}}{4}，x_2=\frac {5-\sqrt{17}}{4}$?
⑤
解?$：(2)x2+2nx+n2=9n2$?
?$(x+n)2=9n2$?
?$x+n=±3n$?
?$x_1=2n，x_2=-4n$?
解:原式?$=\frac {1+x2-1}{x+1}×\frac {(x+1)2}{x2}$?
?$=x+1$?
?$∵x2-2x-3=0$?
?$∴x2-2x+1=4$?
?$(x-1)2=4$?
?$x-1=±2$?
?$x_1=3，x_2=-1$?
?$∵x+1≠0$?
?$∴x≠-1$?
?$∴x=3$?
∴原式?$=3+1=4$?
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