初二数学题

显示全部楼层 · 2010-2-7 21:31:57

1/(m+7)-1/(m+5)=1/(m+8)-1/(m+6)(m+5-m-7)/(m+7)(m+5)=(m+6-m-8)/(m+8)(m+6)-2/(m+7)(m+5)=-2/(m+8)(m+6)(m+7)(m+5)=(m+8)(m+6)m^2+12m+35=m^2+14m+48,m=-13/2检验：m=-13/2是方程的解

千问 · 2010-2-7 21:31:57

左边=（M+6-M-5）/(M^2+11M+30)=1/(M^2+11M+30)右边=（M+8-M-7）/(M^2+15M+56)=1/(M^2+15M+56)左边=右边所以：M^2+11M+30=M^2+15M+56M=-26/4=-13/2

千问 · 2010-2-7 21:31:57

等式左右分别通分后得：（m+5)(m+6)=(m+7)(m+8)m平方+11m+30=m平方+15m+564m=-26m=-6.5

千问 · 2010-2-7 21:31:57

1/(m+5) -1/(m+6)=1/(m+7) -1/(m+8)解:通分得: 1/(m+5)(m+6)=1/(m+7)(m+8)去分母得:(m+5)(m+6)=(m+7)(m+8)去括号得: m^2+11m+30=m^2+15m+56 移项合并同类项得: -4m=26系数化为1得: m=-6.5