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a) 5x7x8x9x10 / 7x8x9x10x11=5/11
b) 3x145+3x55 / 6x215+6x85=3x(145+55)/6x(215+85)=3x200/6x300=3x100x2/3x2x100x3=1/3
\(\frac{5\times7\times8\times9\times10}{7\times8\times9\times10\times11}\)
\(=\frac{5\times\left(7\right)\times\left(8\right)\times\left(9\right)\times\left(10\right)}{\left(7\right)\times\left(8\right)\times\left(9\right)\times\left(10\right)\times11}\)
\(=\frac{5}{11}\)
\(\frac{3\times145+3\times55}{6\times215+6\times85}\)
\(=\frac{3\times\left(145+55\right)}{6\times\left(215+85\right)}\)
\(=\frac{3\times200}{6\times300}\)
\(=\frac{600}{1800}=\frac{1}{3}\)
\(\frac{5\times7\times8\times9\times10}{7\times8\times9\times10\times11}=\frac{5}{11}\)
\(\frac{3\times145+3\times55}{6\times215+6\times85}\)
\(=\frac{3\times\left(145+55\right)}{6\times\left(215+85\right)}\)
\(=\frac{3\times200}{6\times300}\)
\(=\frac{3\times2\times100}{3\times2\times3\times100}\)
\(=\frac{1}{3}\)
=2008x1+2008x1+2008x1+2008x1-2008x4
=2008x(1+1+1+1-4
=2008x0
=0
45 x 22 + 45 x 18
= 45 x ( 18+ 22)
= 45 x 40
= 1000
Đặt :
\(A=\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}\)
\(\Rightarrow2A=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\)
\(\Rightarrow2A=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\)
\(\Rightarrow2A=\frac{1}{3}-\frac{1}{11}\)
\(\Rightarrow2A=\frac{3}{11}\)
\(\Rightarrow A=\frac{3}{22}\)
18/21 +19/32 +3/21+13/32
= (18/21 + 3/21) + (19/32 + 13/32)
= 1 + 1=2
3x145+3x55
=3x(145+55)
=3x200
=600
6x215+6x85
=6x(215+85)
=6x300
=1800
HT nha em
3x145+3x55
=3x(145+55)
=3x200
=600
6x215+6x85
=6x(215+85)
=6x300
=1800
Học Tốt nhoa iem ☘