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電子課本網(wǎng) 第17頁

第17頁

信息發(fā)布者:
解???$:(x-3)[2+3(x-3)]=0$???
???$(x-3)(3x-7)=0$???
???$x-3=0$???或???$3x-7=0$???
???$x_1=3,x_2=\frac {7}{3}$???
解???$:5y(3y-2)=2(3y-2)$???
???$(5y-2)(3y-2)=0$???
???$5y-2=0$???或???$3y-2=0$???
???$y_1=\frac {2}{5},y_2=\frac {2}{3}$???
解???$:(2x-4)2=(5x+15)2$???
???$(5x+15-2x+4)(5x+15+2x-4)=0$???
???$(3x+19)(7x+11)=0$???
???$3x+19=0$???或???$7x+11=0$???
???$x_1=-\frac {19}{3},x_2=-\frac {11}{7}$???
解???$:x2+2\sqrt{5}x+5=0$???
???$(x+\sqrt{5})2=0$???
???$x_1=x_2=-\sqrt{5}$???
解???$:2(8-x)2=(x-8)(x+8)$???
???$(x-8)(x-24)=0$???
???$x-8=0$???或???$x-24=0$???
???$x_1=8,x_2=24$???
解???$:(y-1+3)2=0$???
???$(y+2)2=0$???
???$y_1=y_2=-2$???
解:解答過程有錯,正確的解答過程如下:
把???$x=m$???代入原方程,化簡,得???$\ \mathrm {{m}^3}=m$???
移項,得???$\ \mathrm {{m}^3}-m=0$???
提取公因式???$m,$???得???$m(\ \mathrm {{m}^2}-1)=0$???
由平方差公式,得???$m(m+1)(m-1)=0$???
???$ ∴m=0$???或???$m+1=0$???或???$m-1=0$???
???$ ∴{m}_1=0,$??????${m}_2=-1,$??????${m}_3=1$???
將???$m$???的三個值分別代入原方程檢驗,均符合題意
???$ ∴m $???的值為???$0$???或???$-1$???或???$1$???