3/4+3= 3/4+12/4=15/4

5/2 x 4 =5 x 4/2 = 20/2 = 10

2-7/8=16/8-7/8=9/8

9/4-2=9/4-8/4=1/4

5: 5/7=5 x 7/5= 35/5=7

5/6:2/7=5/6 x 7/2 = 35/12

1/6+2/3 x 8/9= 1/6+ 16/18= 3/18+16/18=19/18

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

                đúng cho mình nhé

1

=1 nhé

Ta có: \(\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{10\times1}\)

\(=2\times\left(\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{5\times6}\right)\)

\(=\frac{2}{11}\times\left(\frac{11}{1\times10}+\frac{11}{2\times9}+\cdots+\frac{11}{5\times6}\right)\)

\(=\frac{2}{11}\times\left(1+\frac12+\frac13+\cdots+\frac19+\frac{1}{10}\right)\)

Ta có: \(A=\frac{1+\frac12+\cdots+\frac{1}{10}}{\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{9\times2}+\frac{1}{10\times1}}\)

\(=\frac{1+\frac12+\cdots+\frac{1}{10}}{\frac{2}{11}\times\left(1+\frac12+\cdots+\frac{1}{10}\right)}=1:\frac{2}{11}=\frac{11}{2}\)

helpppppp meeeeeeee

=5/12+1/24-1/6=11/24-4/24=7/24

\(\dfrac{5}{12}+\dfrac{1}{3.8}-\dfrac{1}{6}\)

\(=\dfrac{5}{12}+\dfrac{1}{24}-\dfrac{1}{6}\)

\(=\dfrac{10}{24}+\dfrac{1}{24}-\dfrac{4}{24}\)

\(=\dfrac{11}{24}-\dfrac{4}{24}\)

\(=\dfrac{7}{24}\)

Ý bạn là như thế này

\(2^{15}.\frac{9^4}{6^3}.8^3=2^{15}\frac{3^8}{3^3.2^3}.2^9=2^{24}.3^5:2^3=2^{21}.3^5=509607936\)

Hay là thế này

\(\frac{2^{15}.9^4}{6^3.8^3}=\frac{2^{15}.3^8}{3^3.2^3.2^9}=\frac{2^{15}.3^8}{3^3.2^{11}}=2^4.3^5=3888\)

Cái nào trong số này là ý của bạn

Cách làm như bạn kia nhưng khi làm bạn ấy làm sai 9 + 3 = 11 ? Thế là kết quả phải ra 1944

\(\frac{2^{15}.9^4}{6^3.8^3}\)

\(=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^3.\left(2^3\right)^3}\)

\(=\frac{2^{15}.3^8}{\left(2^3.2^9\right).3^3}\)

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

\(=2^3.3^5=8.243=1944\)

Ta có: \(1+3+6+10+\cdots+45+55\)

\(=\frac12\times\left(2+6+12+20+\cdots+90+110\right)\)

\(=\frac12\times\left(1\times2+2\times3+\cdots+9\times10+10\times11\right)\)

\(=\frac12\times\left\lbrack1\times\left(1+1\right)+2\times\left(2+1\right)+\cdots+10\times\left(10+1\right)\right\rbrack\)

\(=\frac12\times\left\lbrack\left(1\times1+2\times2+\cdots+10\times10\right)+\left(1+2+\cdots+10\right)\right\rbrack\)

\(=\frac12\times\left\lbrack10\times\left(10+1\right)\times\frac{\left(2\times10+1\right)}{6}+10\times\frac{11}{2}\right\rbrack\)

\(=\frac12\times\left\lbrack10\times11\times\frac{21}{6}+5\times11\right\rbrack=\frac12\times\left\lbrack5\times11\times7+5\times11\right\rbrack\)

\(=\frac12\times5\times11\times\left(7+1\right)=\frac{55}{2}\times8=55\times4=220\)

Ta có: \(1\times10+9\times2+\cdots+10\times1\)

\(=2\times\left(1\times10+2\times9+3\times8+4\times7+5\times6\right)\)

\(=2\times\left\lbrack1\times\left(11-1\right)+2\times\left(11-2\right)+3\times\left(11-3\right)+4\times\left(11-4\right)+5\times\left(11-5\right)\right\rbrack\)

\(=2\times\left\lbrack11\times\left(1+2+3+4+5\right)-\left(1\times1+2\times2+3\times3+4\times4+5\times5\right)\right\rbrack\)

\(=2\times\left\lbrack11\times15-\left(1+4+9+16+25\right)\right\rbrack\)

=2x(165-55)

=2x110

=220

Ta có: \(\frac{1\times10+9\times2+\cdots+10\times1}{1+3+6+10+\cdots+45+55}\)

\(=\frac{220}{220}\)

=1

Ta có: \(\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{10\times1}\)

\(=2\times\left(\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{5\times6}\right)\)

\(=\frac{2}{11}\times\left(\frac{11}{1\times10}+\frac{11}{2\times9}+\cdots+\frac{11}{5\times6}\right)\)

\(=\frac{2}{11}\times\left(1+\frac12+\frac13+\cdots+\frac19+\frac{1}{10}\right)\)

Ta có: \(A=\frac{1+\frac12+\cdots+\frac{1}{10}}{\frac{1}{1\times10}+\frac{1}{2\times9}+\cdots+\frac{1}{9\times2}+\frac{1}{10\times1}}\)

\(=\frac{1+\frac12+\cdots+\frac{1}{10}}{\frac{2}{11}\times\left(1+\frac12+\cdots+\frac{1}{10}\right)}=1:\frac{2}{11}=\frac{11}{2}\)