Cho log26 = a và log35 = b . Hãy tính log12 (căn(20)) theo a,b

A.. ${\log }_{12}\left(\sqrt{20}\right)=\frac{ab-b+2}{2(a+1)}$

B. ${\log }_{12}\left(\sqrt{20}\right)=\frac{ab+b-2}{2(a+1)}$

C. ${\log }_{12}\left(\sqrt{20}\right)=\frac{ab+b-2}{2(a-1)}$

D. ${\log }_{12}\left(\sqrt{20}\right)=\frac{ab-b+2}{2(a-1)}$