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\(\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{3}\right)x\left(1-\frac{1}{4}\right)x\left(1-\frac{1}{5}\right)x\left(1-\frac{1}{6}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}.\frac{5}{6}\)
\(=\frac{1.2.3.4.5}{2.3.4.5.6}=\frac{1}{6}\)
a/
\(1\frac{1}{2}x1\frac{1}{3}x1\frac{1}{4}x1\frac{1}{5}x1\frac{1}{6}=\frac{3}{2}x\frac{4}{3}x\frac{5}{4}x\frac{6}{5}x\frac{7}{6}=\frac{7}{2}=3\frac{1}{2}\)
b/
x=0; y=5
B1 Nhân biểu tthức trên với 1/2 được
1/6+1/12/+1/20+....+1/110=1/2×3+1/3×4+.....+1/10×11
=1/2-1/3+1/3-1/4+.....+1/10-1/11=1/2-1/11=9/22
B2
B.1/1×2+1/2×3+.....+1/99×100=1-1/2 +1/2-1/3+....+1/99-1/100=1-1/100=99/100
Phần a sai đề phải llà1/2×4+1/4×6+.....+1/8×10 mới làm đc nhé
\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{5}\right)\times\left(1-\frac{1}{6}\right)\)
\(=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\)
\(=\frac{1}{6}\)
\(\left(1-\frac{1}{2}\right)\)x \(\left(1-\frac{1}{3}\right)\)x \(\left(1-\frac{1}{4}\right)\)x \(\left(1-\frac{1}{5}\right)\)x \(\left(1-\frac{1}{6}\right)\)
= \(\frac{1}{2}\)x \(\frac{2}{3}\)x \(\frac{3}{4}\)x \(\frac{4}{5}\)x \(\frac{5}{6}\)
= \(\frac{1x2x3x4x5}{2x3x4x5x6}\)
= \(\frac{1}{6}\)
k mình nha
Chúc bạn học giỏi
Mình cảm ơn bạn nhiều
a) 234 x 95 + 234 x 4 + 234 = 234 x ( 95 + 4 + 1 ) = 234 x 100 = 23400
a).234 x 95 + 234 x 4 + 234
= 234 x ( 95 + 4 + 1 )
= 234 x 100
= 23400
b) ( 1+1/2) x ( 1+1/3) x ( 1+1/4 )
= ( 2/2+1/2 ) x ( 3/3+1/3 ) x ( 4/4 + 1/4)
=3/2 + 4/3 + 5/4
= 18/12 + 16/12 + 20/12
= 54/12
= 9 /2
\(\frac{2}{3}.\frac{4}{5}+\frac{1}{3}.\frac{4}{5}=\frac{4}{5}\left(\frac{2}{3}+\frac{1}{3}\right)=\frac{4}{5}.\frac{3}{3}=\frac{4}{5}.1=\frac{4}{5}\)
\(\frac{1}{2}:\frac{3}{4}+\frac{1}{6}:\frac{3}{4}=\frac{3}{4}:\left(\frac{1}{2}+\frac{1}{6}\right)=\frac{3}{4}:\frac{2}{3}=\frac{9}{8}\)
\(\frac{2}{3}.\frac{4}{5}-\frac{1}{3}.\frac{4}{5}=\frac{4}{5}\left(\frac{2}{3}-\frac{1}{3}\right)=\frac{4}{5}.\frac{1}{3}=\frac{4}{15}\)
\(\frac{1}{2}:\frac{3}{4}-\frac{1}{6}:\frac{3}{4}=\frac{3}{4}:\left(\frac{1}{2}-\frac{1}{6}\right)=\frac{3}{4}:\frac{1}{3}=\frac{9}{4}\)
\(\frac{2}{3}.\frac{4}{5}+\frac{1}{3}.\frac{4}{5}=\left(\frac{2}{3}+\frac{1}{3}\right).\frac{4}{5}=1.\frac{4}{5}=\frac{4}{5}\)
\(\frac{1}{2}:\frac{3}{4}+\frac{1}{6}:\frac{3}{4}=\frac{1}{2}.\frac{4}{3}+\frac{1}{6}.\frac{4}{3}=\left(\frac{1}{2}+\frac{1}{6}\right).\frac{4}{3}=\frac{2}{3}.\frac{4}{3}=\frac{8}{9}\)
c,d tương tự
\(1\frac{1}{2}\text{ x }1\frac{1}{3}\text{ x }1\frac{1}{4}\text{ x }1\frac{1}{5}\)
\(=\frac{3}{2}.\frac{4}{3}.\frac{5}{4}.\frac{6}{5}\)
\(=\frac{3.4.5.6}{2.3.4.5}=\frac{6}{2}=3\)
Tính bằng cách thuận tiện nhất :
\(1\frac{1}{2}\cdot1\frac{1}{3}\cdot1\frac{1}{4}\cdot1\frac{1}{5}\)
\(=\left(1\cdot1\cdot1\cdot1\right)\cdot\left(\frac{1}{2}\cdot\frac{1}{3}\cdot\frac{1}{4}\cdot\frac{1}{5}\right)\)
\(=1\cdot\frac{1}{120}\)
\(=\frac{1}{120}\)
\(1\frac{1}{2}:1\frac{1}{3}:1\frac{1}{4}:1\frac{1}{5}\)
\(=\left(1:1:1:1\right):\left(\frac{1}{2}:\frac{1}{3}:\frac{1}{4}:\frac{1}{5}\right)\)
\(=1:30\)
\(=\frac{1}{30}\)
Đáp số : \(\frac{1}{5}\)
Tk mk mk tk lại ! ^^
= 1/2 x 2/3 x 3/4 x4/5
= 1x2x3x4/ 2x3x4x5
=1/5