\(\frac{7^2}{2.9}+\frac{7^2}{9.16}+...+\frac{7^2}{65.72}\)

\(=7^2\left(\frac{1}{2.9}+\frac{1}{9.16}+...+\frac{1}{65.72}\right)\)

\(=\frac{7^2}{7}\left(\frac{1}{2}-\frac{1}{9}+\frac{1}{9}-\frac{1}{16}+...+\frac{1}{65}-\frac{1}{72}\right)\)

\(=7\left(\frac{1}{2}-\frac{1}{72}\right)\)

\(=7.\frac{35}{72}\)

\(=\frac{245}{72}\)

\(a,=\left(576-577\right)+\left(678-679\right)+\left(780-475\right)=-1-1+305=303\\ b,=158\times0=0\\ c,=12\left(36\times17\times34+15\right)=12\times20823=249876\)

\(A=\frac{2^{12}.27^3}{6^7.16^2}=\frac{2^{12}.3^9}{3^7.2^{15}}=\frac{3^2}{2^3}=\frac{9}{8}\)

\(A=\frac{2^{12}.27^3}{6^7.16}=\frac{2^{12}.3^9}{3^7.2^{15}}=\frac{3^2}{2^3}=\frac{9}{8}\)

~Hok tốt~

\(A=\frac{2^{12}.27^3}{6^7.16^2}\)

\(=\frac{2^{12}.3^9}{2^7.3^7.2^8}\)

\(=\frac{2^{12}.3^9}{2^{15}.3^7}=\frac{3^2}{2^3}=\frac{8}{9}\)

72 : 8 + 16

= 9 + 16

= 25

C

C

c