計算√18-√9/2

計算√18-√9/2


√18-√9/2
=3√2-3√2/2
=3√2/2



計算:12m2-9+23-m+2m+3.


12m2-9+23-m+2m+3=12(m+3)(m-3)+-2(m+3)(m+3)(m-3)+2(m-3)(m+3)(m-3)=12-2(m+3)+2(m-3)(m+3)(m-3)=12-2m-6+2m-6(m+3)(m-3)=0



計算:m-21/m^2-9 - 3/3-m
另:


(m-21)/(m^2-9)-3/(3-m)
=(m-21)/(m^2-9)+3(m+3)/(m^2-9)
=(m-21+3m+9)/(m^2-9)
=(4m-12)/(m^2-9)
=4(m-3)/(m+3)(m-3)
=4/(m+3)