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\(\frac{9}{8}\)x \(\frac{16}{15}\)x \(\frac{25}{24}\)x \(\frac{36}{35}\)x\(\frac{49}{48}\)x\(\frac{64}{63}\)x\(\frac{81}{80}\)
= \(\frac{3x3}{2x4}\)x \(\frac{4x4}{3x5}\)x\(\frac{5x5}{4x6}\)x\(\frac{6x6}{5x7}\)x\(\frac{7x7}{6x8}\)x\(\frac{8x8}{7x9}\)x\(\frac{9x9}{8x10}\)
= \(\frac{3x3x4x4x5x5x6x6x7x7x8x8x9x9}{2x4x3x5x4x6x5x7x6x8x7x9x8x10}\)
= \(\frac{3x9}{2x10}\)
= \(\frac{27}{20}\)
Ta phân tích: 4/3=2/1x2/3;9/8=3/2x3/4;16/15=4/3x4/5;.......;99/98x99/100, Ta có dãy số:2/1x2/3x3/2x3/4x4/3x4/5x........x99/98x99/100. Xóa bớt những tử số và mẫu số giống nhau, ta có kết quả bằng: 2/1x99/100= 2x99/100=99/50
a) \(\frac{1}{8}+\frac{3}{5}=\frac{5+24}{40}=\frac{29}{40}\)
b) \(\frac{6}{35}.\frac{49}{54}+\frac{1}{3}=\frac{6.7.7}{5.7.6.9}+\frac{1}{3}=\frac{7}{45}+\frac{1}{3}=\frac{7}{45}+\frac{15}{45}=\frac{22}{45}\)
c) \(\frac{4}{5}:\frac{3}{4}+0,25=\frac{4}{5}.\frac{4}{3}+\frac{25}{100}=\frac{16}{15}+\frac{1}{4}=\frac{64+15}{60}=\frac{79}{60}\)
`@Neo`
\(\dfrac{25\times17-24}{26+15\times25}\)
\(=\dfrac{25\times15+25\times2-24}{26+15\times25}\)
\(=\dfrac{25\times15+50-24}{26+15\times25}\)
\(=\dfrac{25\times15+26}{26+15\times25}=1\)
39x49 - 1 trên 35x48 + 34
Tính bằng cách thuật tiện nhất. Ạ
A = \(\dfrac{4}{3}\times\dfrac{9}{8}\times\dfrac{16}{15}\times\dfrac{25}{24}\times\dfrac{36}{35}\times\dfrac{49}{48}\times\dfrac{64}{63}\times\dfrac{81}{80}\times\dfrac{100}{99}\times\dfrac{121}{120}\)
A = \(\dfrac{2\times2\times3\times3\times4\times4\times5\times5\times6\times6\times7\times7\times8\times8\times9\times9\times10\times10\times11\times11}{1\times3\times2\times4\times3\times5\times4\times6\times5\times7\times6\times8\times7\times9\times8\times10\times9\times11\times10\times12}\)
A = \(\dfrac{3\times3\times4\times4\times5\times5.....\times10\times10}{3\times3\times4\times4\times5\times5.....\times10\times10}\) \(\times\) \(\dfrac{2\times2\times11\times11}{1\times2\times11\times12}\)
A =1 \(\times\) \(\dfrac{2\times2\times11\times11}{1\times2\times11\times2\times6}\)
A = \(\dfrac{2\times2\times11}{2\times2\times11}\) \(\times\) \(\dfrac{11}{6}\)
A = 1 \(\times\) \(\dfrac{11}{6}\)
A = \(\dfrac{11}{6}\)