tính A1x2x3+2x4x6+3x6x9
Những câu hỏi liên quan
1x2x3 + 2x4x6 + 3x6x9/2x3x4 + 4x6x8 + 6x9x12
1x2x3+2x4x6+3x6x9+4x8x12/2x3x4+4x6x8+6x9x12+8x12x16
\(\frac{1x2x3+3x6x9+5x10x15}{2x4x6+6x12x18+10x20x30}\)
\(\frac{\frac{1}{3}+\frac{1}{7}-\frac{1}{21}+\frac{1}{35}}{\frac{2}{3}+\frac{2}{7}-\frac{2}{21}+\frac{2}{35}}\)
\(\frac{0,25+\frac{1}{9}-\frac{1}{11}}{0,75+\frac{1}{3}-\frac{3}{11}}+\frac{2}{3}\)
Bài 5 : Tính nhanh : a , \(A=\frac{1x2x3+2x4x6+3x6x9}{1x3x5+2x6x10+3x9x15}\)
Bài 5 : Tính nhanh a , \(A=\frac{1x2x3+2x4x6+3x6x9}{1x3x5+2x6x10+3x9x15}\)
\(A=\frac{1.2.3+2.4.6+3.6.9}{1.3.5+2.6.10+3.9.15}=\frac{2\left(1.3+2.2.6+3.3.9\right)}{5\left(1.3+2.2.6+3.3.9\right)}=\frac{2}{5}\)
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46656/729000
bn tự rút gon nhé k mik nha CHUC BN HOC GIOI
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Tính 1x2x3+2x4x6+4x8x12+7x14x21/1x3x5+2x6x10+4x12x20+7x21x35
\(\dfrac{1\times2\times3+2\times4\times6+4\times8\times12+7\times14\times21}{1\times3\times5+2\times6\times10+4\times12\times20+7\times21\times35}\\ =\dfrac{1\times2\times3}{1\times3\times5}+\dfrac{2\times4\times6}{2\times6\times10}+\dfrac{4\times8\times12}{4\times12\times20}+\dfrac{7\times14\times21}{7\times21\times35}\\ =\dfrac{2}{5}+\dfrac{4}{10}+\dfrac{8}{20}+\dfrac{14}{35}\\ =\dfrac{2}{5}+\dfrac{2}{5}+\dfrac{2}{5}+\dfrac{2}{5}\\ =\dfrac{2}{5}\times4\\ =\dfrac{8}{5}\)
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Tính tổng
cho P=2x4x6+4x6x8+6x8x10+...+94x96x98+96x98x100
Ta có G = 2 . 4 + 4 . 6 + 6 . 8 + ... + 98 . 100
6 . G = 2 . 4 . 6 + 4 . 6 . 6 + 6 . 8 . 6 + .... + 98 . 100 . 6
6 . G = 2 . 4 . 6 + 4 . 6 . ( 8 - 2 ) + 6 . 8 . ( 10 - 4 ) + .... + 98 . 100 . ( 102 - 96 )
6 . G = 2 . 4 . 6 + 4 . 6 . 8 - 2 . 4 . 6 + 6 . 8 . 10 - 4 . 6 . 8 + ... + 98 .100 . 102 - 96 . 98 . 100
6 . G = 98 . 100 . 102
G = 98 . 100 . 102 : 6
G = 999 600 : 6
G = 166 600
Ta có G = 2 . 4 + 4 . 6 + 6 . 8 + ... + 98 . 100
6 . G = 2 . 4 . 6 + 4 . 6 . 6 + 6 . 8 . 6 + .... + 98 . 100 . 6
6 . G = 2 . 4 . 6 + 4 . 6 . ( 8 - 2 ) + 6 . 8 . ( 10 - 4 ) + .... + 98 . 100 . ( 102 - 96 )
6 . G = 2 . 4 . 6 + 4 . 6 . 8 - 2 . 4 . 6 + 6 . 8 . 10 - 4 . 6 . 8 + ... + 98 .100 . 102 - 96 . 98 . 100
6 . G = 98 . 100 . 102
G = 98 . 100 . 102 : 6
G = 999 600 : 6
G = 166 600
Tính tổng: 1/(2x4x6) + 1/(4x6x8) + 1/(6x8x10) +...+ 1/(96x98x100)
\(=\frac{49\times50-1}{4\times98\times100}\)
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Tính nhanh
1/2x4x6 +1/4x6x8 + 1/6x8x10 + 1/8x10x12 + ...+ 1/96x98x100
Đặt biểu thức là A
\(4xA=\frac{4}{2x4x6}+\frac{4}{4x6x8}+\frac{4}{6x8x10}+\frac{4}{8x10x12}+...+\frac{4}{94x96x98}+\frac{4}{96x98x100}\)
\(4xA=\frac{6-2}{2x4x6}+\frac{8-4}{4x6x8}+\frac{10-6}{6x8x10}+\frac{12-8}{8x10x12}+...+\frac{98-94}{94x96x98}+\frac{100-96}{96x98x100}\)
\(4xA=\frac{1}{2x4}-\frac{1}{4x6}+\frac{1}{4x6}-\frac{1}{6x8}+\frac{1}{6x8}-\frac{1}{8x10}+...+\frac{1}{94x96}-\frac{1}{96x98}+\frac{1}{96x98}-\frac{1}{98x100}\)
\(4xA=\frac{1}{2x4}-\frac{1}{98x100}=\frac{49x50-1}{98x100}\Rightarrow A=\frac{49x50-1}{4x98x100}\)
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