Tính \(M=2^1\times4^2\times6^3\times...\times100^{50}\)
Tính nhanh:
C=\(\frac{3}{2\times3\times4}+\frac{3}{3\times4\times5}+\frac{3}{4\times5\times6}+......+\frac{3}{98\times99\times100}\)
C = \(\frac{3}{2.3.4}+\frac{3}{3.4.5}+.....+\frac{3}{98.99.100}\)
C = \(3.\left(\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{98.99.100}\right)\)
C = \(3.\frac{1}{2}.\left(\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{98.99.100}\right)\)
C = \(\frac{3}{2}.\left(\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{100-98}{98.99.100}\right)\)
C = \(\frac{3}{2}.\left(\frac{4}{2.3.4}-\frac{2}{2.3.4}+\frac{5}{3.4.5}-\frac{3}{3.4.5}+...+\frac{100}{98.99.100}-\frac{99}{98.99.100}\right)\)
C = \(\frac{3}{2}.\left(\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{98.99}-\frac{1}{99.100}\right)\)
C = \(\frac{3}{2}.\left(\frac{1}{2.3}-\frac{1}{99.100}\right)\)
C = \(\frac{3}{2}.\frac{1649}{9900}\)
C = \(\frac{1649}{6600}\)
Hồ Thu Giang cần chứ nếu được cảm ơn nha
Tính nhanh: D=\(\frac{4}{2\times3\times4}+\frac{4}{3\times4\times5}+\frac{4}{4\times5\times6}+.......+\frac{4}{98\times99\times100}\)
CHO A = \(\frac{2\times9\times8+3\times12\times10+4\times15\times12+...+98\times297\times200}{2\times3\times4+3\times4\times5+4\times5\times6+...+98\times99\times100}\)
TÍNH A\(^2\)
\(A=\frac{2\cdot9\cdot8+3\cdot12\cdot10+4\cdot15\cdot12+...+98\cdot297\cdot200}{2\cdot3\cdot4+3\cdot4\cdot5+4\cdot5\cdot6+...+98\cdot99\cdot100}\)
\(=\frac{2\cdot1\cdot3\cdot3\cdot4\cdot2+3\cdot1\cdot4\cdot3\cdot5\cdot2+...+98\cdot1+99\cdot3+100\cdot2}{2\cdot3\cdot4+3\cdot4\cdot5+...+98\cdot99\cdot100}\)
\(=\frac{1\cdot3\cdot2\cdot\left(2\cdot3\cdot4+3\cdot4\cdot5+...+98\cdot99\cdot100\right)}{2\cdot3\cdot4+3\cdot4\cdot5+...+98\cdot99\cdot100}\)
\(=1\cdot3\cdot2\)
\(=6\)
\(A^2=6^2=36\)
P = \(2\times3+3\times4+4\times5+5\times6+...+99\times100\)
P = 2 x 3 + 3 x 4 + ...+ 99 x 100
=> 3 x P = 2 x 3 x 3 + 3 x 4 x 3 + ....+ 99 x 100 x 3
3 x P = 2 x 3 x ( 4-1) + 3 x 4 x (5-2) + ...+ 99 x 100 x ( 101 -98)
3 x P = 2 x 3 x 4 - 1 x 2 x 3 + 3 x 4 x 5- 2 x 3 x 4 + ...+ 99 x 100 x 101 - 98 x 99 x 101
3 x P = ( 2 x 3 x 4 + 3 x 4 x 5 + ...+ 99 x 100 x 101) - ( 1 x 2 x 3 + 2 x 3 x 4 + ...+ 98 x 99 x 101)
3 x P = 99 x 100 x 101 - 1 x 2 x 3
\(P=\frac{99x100x101-1x2x3}{3}=333298\)
p=2.3+3.4+4.5+5.6+...+99.100
3p=2.3.3+3.4.3+4.5.3+5.6.3+...+99.100.3
3p=2.3.(4-1)+3.4.(5-2)+4.5.(6-3)+5.6.(7-4)+...+99.100.(101-98)
3p=2.3.4-1.2.3+3.4.5-2.3.4+4.5.6-3.4.5+5.6.7-4.5.6+99.100.101-98.99.100
3p=98.99.100-1.2.3
p=\(\frac{98.99.100-1.2.3}{3}=323398\)
\(\frac{1}{2\times4}+\frac{1}{4\times6}+\frac{1}{6\times8}+.....+\frac{1}{98\times100}=....\)
nhân biểu thức vs 2. đcj bao nhiêu chia cho 2
Tính:
\(A=\frac{1^2}{1\times2}\times\frac{2^2}{2\times3}\times\frac{3^2}{3\times4}\times...\times\frac{99^2}{99\times100}\times\frac{100^2}{100\times101}\)
Ta có:
\(A=\frac{1^2}{1.2}.\frac{2^2}{2.3}.\frac{3^2}{3.4}...\frac{99^2}{99.100}.\frac{100^2}{100.101}\)
\(=\frac{1}{2}.\frac{4}{6}.\frac{9}{12}....\frac{9801}{9900}.\frac{10000}{10100}\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{99}{100}.\frac{100}{101}=\frac{1.2.3...99.100}{2.3.4...100.101}=\frac{1}{101}\)(Tối giản)
\(\frac{1}{2\times4}+\frac{1}{4\times6}+\frac{1}{6\times8}+\cdot\cdot\cdot+\frac{1}{96\times98}+\frac{1}{98\times100}\)= ?
\(S.2=\frac{2}{2.4}+\frac{2}{4.6}+...........+\frac{2}{98.100}\)
\(S.2=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+.....+\frac{1}{98}-\frac{1}{100}\)
\(S.2=\frac{1}{2}-\frac{1}{100}\)
\(S.2=\frac{49}{100}\)
\(S=\frac{49}{100}:2\)
\(S=\frac{49}{200}\)
\(A=\frac{1}{1\times2}+\frac{1}{3\times4}+\frac{1}{5\times6}+...+\frac{1}{99\times100}.CMR:\frac{7}{12}< A< \frac{5}{6}\)
S =\(\frac{1}{2\times4}\)+\(\frac{1}{4\times6}+\frac{1}{6\times8}+...+\frac{1}{96\times98}+\frac{1}{98\times100}\)