\(27^{10}+3^{29}+9^{14}=3^{30}+3^{29}+3^{28}=3^{28}\cdot\left(3^2+3+1\right)=3^{28}\cdot13\)chia hết cho 13

\(27^{10}+3^{29}+9^{14}\)

\(=\left(3^3\right)^{10}+3^{29}+\left(3^2\right)^{14}\)

\(=3^{30}+3^{29}+3^{28}\)

\(=3^{28}.\left(3^2+3+1\right)\)

\(=3^{28}.\left(9+3+1\right)\)

\(=3^{28}.13\)chia hết cho 13

=> đpcm

Ủng hộ mk nha ^_-

b)\(\frac{3}{4}x-\frac{1}{8}=\frac{3}{7}\)\(\Leftrightarrow\frac{3}{4}x=\frac{3}{7}+\frac{1}{8}=\frac{31}{56}\)\(\Leftrightarrow x=\frac{31}{56}:\frac{3}{4}=\frac{31}{42}\)

c)\(-\frac{21}{13}x+\frac{1}{3}=\frac{2}{3}\Leftrightarrow-\frac{21}{13}x=\frac{2}{3}-\frac{1}{3}=\frac{1}{3}\Leftrightarrow x=\frac{1}{3}:-\frac{21}{13}=-\frac{13}{63}\)

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{6480}\)

\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{80.81}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{80}-\frac{1}{81}=1-\frac{1}{81}=\frac{80}{81}\)

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{6480}\)

\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{80.81}\)

\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{80}-\frac{1}{81}\)

\(A=1-\frac{1}{81}\)

\(A=\frac{80}{81}\)

Cái này là toán lớp 6 nha bn

Ủng hộ mk nha ^_-

giup minh nhanh nhe

thì bằng 1 thôi , vì 16480.1 chỉ có thể bằng 16480 

Tổng 3 góc trong 1 tam giác là 180 dộ 

góc A- góc C=18+18=36 độ

Góc C là: (180-18-36):3=42độ 

Góc B là : 42+18=60 độ 

Góc A là : 60+18=78 độ

Cảm ơn ạ 

thiếu đề

Thiếu đề nha bn

\(\frac{a+5}{a-5}=\frac{b+6}{b-6}\) => (a + 5)(b - 6) = (a - 5)(b + 6) => ab - 6a + 5b - 30 = ab + 6a - 5b - 30 

=>\(-6a+5b\) = 6a - 5b =\(-\left(6a-5b\right)\)  => 6a - 5b = 0 => 6a = 5b => \(\frac{a}{b}=\frac{5}{6}\)(đpcm)

\(\frac{a+5}{a-5}=\frac{b+6}{b-6}\Rightarrow\frac{a+5}{b+6}=\frac{a-5}{b-6}=\frac{2a}{2b}=\frac{a}{b}\)

Suy ra:\(\frac{a+5}{b+6}=\frac{a}{b}\Rightarrow a.\left(b+6\right)=b.\left(a+5\right)\)

=>ab+6a=ab+5b

=>6a=5b

=>\(\frac{a}{b}=\frac{5}{6}\)