5/15+14/25-12/9+2/7+11/25=(5/15+2/7)+(14/25+11/25)-12/9=17/35+1-12/9=16/105

=\(\left(\frac{5}{15}-\frac{12}{9}\right)+\left(\frac{14}{25}+\frac{11}{15}\right)+\frac{2}{7}\)

=\(\left(\frac{1}{3}-\frac{4}{3}\right)+1+\frac{2}{7}\)

=\(\frac{-3}{3}+1+\frac{2}{7}=-1+1+\frac{2}{7}\)

=\(\frac{2}{7}\)

\(\frac{8^4.3^5-4^6.9^3}{4^6.9^3+4^8.3^5}=\frac{8^4}{4^8}=\frac{4096}{65536}=\frac{1}{16}\)

k nha 

\(\frac{8^4.3^5-4^6.9^3}{4^6.9^3+4^8.3^5}=\frac{2^{12}.3^5-2^{12}.3^6}{2^{12}.3^6+2^{16}.3^5}=\frac{2^{12}.3^5\left(1-3\right)}{2^{12}.3^5\left(3-2\right)}=\frac{-2}{1}\) = -2

Xin một câu quote nha! ^^

c) (0.01):2,5=(0,75x).(0,75)

         0,004 =(0,75x).(0,75)

         => x=0.0071

Đề này bn xem lại coi có đúng k

bai 1

\(\frac{7}{4}\)+ \(\frac{5}{6}\):5 - 0,375.2.\(^{\left(-2\right)^2}\)= \(\frac{7}{4}\)+ \(\frac{5}{6}\)x\(\frac{1}{5}\)- \(\frac{15}{4}\). 2.4=\(\frac{7}{4}\)+\(\frac{1}{6}\)-\(\frac{15}{4}\).8=\(\frac{42}{24}\)+\(\frac{4}{24}\)-30=\(\frac{11}{6}\)-30=-169/6

\(\frac{1}{4}\)+\(\frac{3}{4}\). \(\left(\frac{-1}{2}+\frac{2}{3}\right)\)=\(\frac{1}{4}\)+ \(\frac{3}{4}\).\(\left(\frac{-3}{6}+\frac{4}{6}\right)\)= \(\frac{1}{4}+\frac{3}{4}.\frac{1}{6}=\frac{1}{4}+\frac{3}{8}\)= \(\frac{5}{8}\)

Ảnh hơi mờ 

\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}=\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)}{\left(-5\right)^{20}.3^{10}.3^2}=\frac{-5}{3^2}=-\frac{5}{9}\)

\(\frac{0,8\div\left(\frac{4}{5}\cdot1,25\right)}{0,64-\frac{1}{25}}+\left(1,2\cdot0,5\right)\div\frac{3}{5}\)

\(=\frac{0,8\div\left(0,8\cdot1,25\right)}{0,64-0,04}+\left(1,2\cdot0,5\right)\div0,6\)

\(=\frac{0,8\div1}{0,6}+0,6\div0,6\)

\(=\frac{0,8}{0,6}+1\)

\(=\frac{4}{3}+1=\frac{7}{3}\)

\(\frac{0,8\div\left(\frac{4}{5}\cdot1,25\right)}{0,64-\frac{1}{25}}+\left(1,2\cdot0,5\right)\div\frac{3}{5}\)

\(=\frac{0,8\div\left(0,8.1,25\right)}{0,64-0,04}+\left(1,2.0,5\right)\div0,6\)

\(=\frac{0,8\div1}{0,6}+0,6\div0,6\)

\(=\frac{4}{3}+1\)

\(=\frac{7}{3}\)

(1 - 1/2) x (1 - 1/3) x (1 - 1/4) x (1 - 1/5) x (1 - 1/6)

= 1/2 x 2/3 x 3/4 x 4/5 x 5/6

= 1/6 (tử và mẫu triệt tiêu cho nhau)